More docs

Author: matklad

docs/TOOLS.md

@@ -17,14 +17,20 @@ cargo tool
 ```
 
 
-# Tool: `gen`
+## Tool: `gen`
 
 This tool reads a "grammar" from [grammar.ron](../grammar.ron) and
 generates the `syntax_kinds.rs` file. You should run this tool if you 
 add new keywords or syntax elements.
 
 
-# Tool: 'parse'
+## Tool: `parse`
 
 This tool reads rust source code from the standard input, parses it,
 and prints the result to stdout.
+
+
+## Tool: `collect-tests`
+
+This tools collect inline tests from comments in libsyntax2 source code
+and places them into `tests/data/inline` directory.