Update typescript-eslint config

[DylanSp]

1. @typescript-eslint/eslint-plugin and @typescript-eslint/parser need to be upgraded to at least v6 to avoid this error:

DeprecationError: 'originalKeywordKind' has been deprecated since v5.0.0 and can no longer be used. Use 'identifierToKeywordKind(identifier)' instead
See typescript-eslint/typescript-eslint#7155 (comment).

2. Starting with v6, typescript-eslint's recommended configuration has changed somewhat; there's also apparently configurations that can leverage type checking that would be worth looking at. See the v6 announcement for details. I probably want to switch from just recommended to recommended-type-checked and stylistic-type-checked (assuming the latter works fine with Prettier).