Update developer documentation to provide extra ANTLR instructions

[jimidle]

Adds additional instructions for making ANTLR grammar changes, including explicit rules and checks to make.

[github-actions[bot]]

Coverage tests results

401 tests  ±0   194 :white_check_mark: ±0   4s :stopwatch: ±0s   2 suites ±0     0 :zzz: ±0    2 files   ±0   207 :x: ±0 

For more details on these failures, see this check.

Results for commit 8491b6fa. ± Comparison against base commit bd18476f.

:recycle: This comment has been updated with latest results.

[jimidle]

Docs greatly expanded with examples and screenshots, as well as explanations of various parts of grammar files.