docs: fix grammar and spelling mistakes

- Normalized "`setting`: description" spacing across the settings list
  (was inconsistently "`setting` : description" in many entries).
- Fixed "eg." -> "e.g.", "3rd party" -> "third-party", and a handful of
  other grammar/wording issues in README.md and USAGE_DATA.md.
- Fixed invalid JSON in the java.configuration.runtimes example
  (trailing commas before a closing brace/bracket).

Rebased onto current main and reapplied by hand: the original diff
conflicted with settings/runtime entries added upstream since this PR
was opened. Picked up the same JSON trailing-comma issue on the newly
added JavaSE-27 entry and the newly added
java.referencesCodeLens.includeFields spacing issue while at it, and
kept "default": true on JavaSE-25 (removing it wasn't necessary for
valid JSON and conflicts with main's later intent of showing multiple
default-marked entries as an example).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Author: 2 people