Add a couple section headers in language overview doc (#5175)

docs/language/overview.md

@@ -17,7 +17,7 @@ by a number of commands:
 command | command | command | ...
 ```
 However, in Zed, the entities that transform data are called
-"operators" instead of "commands" and unlike Unix pipelines,
+"[operators](operators/README.md)" instead of "commands" and unlike Unix pipelines,
 the streams of data in a Zed query
 are typed data sequences that adhere to the
 [Zed data model](../formats/zed.md).
@@ -48,6 +48,8 @@ and the Zed compiler optimizes the data flow computation
 the flow implied by the pipeline yet reaching the same result —
 much as a modern SQL engine optimizes a declarative SQL query.
 
+## Search and Analytics
+
 Zed is also intended to provide a seamless transition from a simple search experience
 (e.g., typed into a search bar or as the query argument of the [`zq`](../commands/zq.md) command-line
 tool) to more a complex analytics experience composed of complex joins and aggregations
@@ -95,6 +97,8 @@ The short-hand query from above might be typed into a search box while the
 latter query might be composed in a query editor or in Zed source files
 maintained in GitHub.  Both forms are valid Zed queries.
 
+## Comments
+
 To further ease the maintenance and readability of source files, comments
 beginning with `//` may appear in Zed.