Rewrite scripts/docs.js

The funcs.md file had diverged quite a lot from what the script
generated. The new script means we can again autogenerate funcs.md
from the hydra-synth/src/composable-glsl-functions.js file.

docs/funcs.md.template

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+{{! This is a mustache template for the Hydra function documentation.
+    The funcs.md file is generated by `scripts/docs.js` using this template.
+}}
+# Functions
+
+- [Categories of functions](#categories)
+- [Complete contents of functions](#contents)
+
+## Categories
+
+- [Audio](#audio)
+- [Color](#color)
+- [Geometry](#geometry)
+- [Global variables](#global-variables)
+- [Modulators](#modulators)
+- [Operators](#operators)
+- [Sources](#sources)
+- [Parameter sequences](#parameter-sequences)
+
+## Contents
+
+- [Audio](#audio)
+  - [hide](#hide)
+  - [setBins](#setbins)
+  - [setCutoff](#setcutoff)
+  - [setScale](#setScale)
+  - [setSmooth](#setSmooth)
+  - [show](#show)
+- [Color](#color)
+{{ category-toc-color }}
+- [Geometry](#geometry)
+{{ category-toc-geometry }}
+- [Global variables](#global-variables)
+  - [mouse](#mouse)
+  - [time](#time)
+- [Modulators](#modulators)
+{{ category-toc-modulators }}
+- [Operators](#operators)
+{{ category-toc-operators }}
+- [Sources](#sources)
+{{ category-toc-sources }}
+  - [out](#out)
+  - [render](#render)
+- [Parameter sequences](#parameter-sequences)
+  - [Lists as parameter sequences](#lists-as-parameter-sequences)
+  - [Functions on parameter sequences](#functions-on-parameter-sequences)
+    - [fast](#fast)
+
+---
+
+## Audio
+
+Functions for manipulating audio signals.
+
+- [hide](#hide)
+- [setBins](#setbins)
+- [setCutoff](#setcutoff)
+- [setScale](#setScale)
+- [setSmooth](#setSmooth)
+- [show](#show)
+
+### hide
+
+`.hide()`
+
+### setBins
+
+`.setBins( bins )`
+
+* `bins` :: integer (default `x`)
+
+### setCutoff
+
+`.setCutoff( frequency )`
+
+* `frequency` :: float (default `x`)
+
+### setScale
+
+`.setScale( amount )`
+
+* `amount` :: float (default `x`) 
+
+### setSmooth
+
+`.setSmooth( amount )`
+
+* `amount` :: float (default `x`)
+
+### show
+
+`.show()`
+
+---
+
+## Color
+
+Functions for manipulating color.
+
+{{ category-toc-color }}
+
+{{& functions-color }}
+
+---
+
+## Geometry
+
+Functions for manipulating geometry.
+
+{{ category-toc-geometry }}
+
+{{& functions-geometry }}
+
+---
+
+## Global variables
+
+Useful variables that are defined globally, and can be used within functions as a parameter.
+
+- [mouse](#mouse)
+- [time](#time)
+
+### mouse
+
+`mouse`
+
+* `.x` :: x position of mouse
+* `.y` :: y position of mouse
+
+#### Example
+
+Control the oscillator frequency with the mouse position:
+
+```javascript
+osc(() => mouse.x).out(o0)
+```
+
+### time
+
+`time`
+
+* `time` :: the current time
+
+#### Example
+
+Control the oscillator using a sine wave based on the current time:
+
+```javascript
+osc( ({time}) => Math.sin(time) ).out(o0)
+```
+
+---
+
+## Modulators
+
+Functions for describing modulations of sources. 
+
+{{ category-toc-modulators }}
+
+{{& functions-modulators }}
+
+## Operators
+
+Functions for performing operations on sources.
+
+{{ category-toc-operators }}
+
+{{& functions-operators }}
+
+---
+
+## Sources
+
+Sources are elementary generators that output different types of visual content.
+
+{{ category-toc-sources }}
+  - [out](#out)
+  - [render](#render)
+
+{{& functions-sources }}
+
+### out
+
+`.out( buffer )`
+
+* `buffer`
+  * `osc`: `o0`, `o1`, `o2`, `o3`
+  * `src`: `s0`, `s1`, `s2`, `s3`
+
+#### Example
+
+```javascript
+// output four oscillators to different buffers
+// and then modulate them together
+osc( [1,10,50,100,250,500].fast(2) ).kaleid(20).out(o0) // frequency
+osc( ({time}) => Math.sin(time/10) * 100 ).kaleid(19).out(o1) // frequency 2
+osc( 10, [-10,-1,-0.1,0,0.1,1,10], 0 ).kaleid(21).out(o2) // sync
+osc(10,0.1, ({time}) => Math.sin(time/10) * 1 ) // offset
+  .modulate(o1,0.05)
+  .modulate(o2,0.05)
+  .modulate(o3,0.05)
+  .kaleid(20)
+  .add(noise(3,10))
+  .out(o3)
+render(o3)
+```
+
+### render
+
+`render( buffer )`
+
+* `buffer`: buffer (default `o0`)
+
+#### Example
+
+```javascript
+osc( [1,10,50,100,250,500].fast(2) ).out(o0) // frequency
+osc( ({time}) => Math.sin(time/10) * 100 ).out(o1) // frequency 2
+osc( 10, [-10,-1,-0.1,0,0.1,1,10], 0 ).out(o2) // sync
+osc(10,0.1, ({time}) => Math.sin(time/10) * 100 ).out(o3) // offset
+
+render(o0) // change to o1, o2, or o3
+```
+
+```javascript
+// see all four buffers at once
+osc( [1,10,50,100,250,500].fast(2) ).out(o0) // frequency
+osc( ({time}) => Math.sin(time/10) * 100 ).out(o1) // frequency 2
+osc( 10, [-10,-1,-0.1,0,0.1,1,10], 0 ).out(o2) // sync
+osc(10,0.1, ({time}) => Math.sin(time/10) * 100 ).out(o3) // offset
+render()
+```
+
+---
+
+## Parameter sequences
+
+- [Lists as parameter sequences](#lists-as-parameter-sequences)
+- [Functions on parameter sequences](#functions-on-parameter-sequences)
+    - [fast](#fast)
+
+### Lists as parameter sequences
+
+```
+osc(
+   [80, 100, 200, 50], 1 )
+)
+.out(o0)
+```
+
+### Functions on parameter sequences
+
+#### fast
+
+`fast ( amount) `
+
+* `amount` :: float (default `x`)
+
+```
+osc(
+   [80, 100, 200, 50].fast(0.2), 1 )
+)
+.out(o0)
+```