[FR]: Allow opt-in with tags in addition to existing 'nolint' opt-out

### What is the current behavior?

This feature does not exist today.

### Describe the feature

Currently, when we introduce a lint, there is now support to [opt-out with `no-lint`](github.com/aspect-build/rules_lint/blob/main/docs/linting.md#ignoring-targets).

When introducing linter(s) in a larger repository, it'd be easier if the opposite were possible, i.e. a `lint`-like opt-in tag where the linter runs ONLY on those targets.

Even nicer if possible to opt-in per linter. For eg., `lint-`

Start with docs/linting.md and its existing no-lint behavior. Trace how lint-related target tags are handled, then define the opt-in and per-linter tag behavior described in the issue. Done means linting runs only for opted-in targets, with per-linter opt-in supported if feasible, and the documentation reflects the behavior.

Written by the indexing model from the issue text.