fix(snippets): escape literal $

[dezza]

Continuation and more complete version of #1181

Adds literal $ escaping for the rest of the snippets. Without the literal escaping parsing code for placeholders is significantly more complex (magic 🧙) and incompatible with various lsp clients with snippet functionality for vim and other editors.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.91%. Comparing base (c4cccaf) to head (1fce98a).
Report is 11 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1258   +/-   ##
=======================================
  Coverage   80.91%   80.91%           
=======================================
  Files          29       29           
  Lines        1441     1441           
  Branches      344      344           
=======================================
  Hits         1166     1166           
  Misses        221      221           
  Partials       54       54           

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