[FR]: example of a plugin compiled from Rust

### What is the current behavior?

Followup to #149 which introduces plugin support but only documents how to use them for pre-built plugins distributed as wasm files.

### Describe the feature

https://github.com/aspect-build/rules_swc/pull/149#issuecomment-1422987161 suggests that users ought to be able to use rules_rust to have their plugin code live in the monorepo alongside the swc_plugin rule.

/cc @realtimetodie @titanous

### Fund our work

- [ ] Sponsor our open source work by donating a [feature bounty](https://opencollective.com/aspect-build/)

Read follow-up issue #149 and the linked pull-request discussion first, then inspect the existing swc_plugin rule and rules_rust integration points. A complete change would provide a documented, working example of a Rust plugin compiled from the monorepo alongside the rule, rather than only using a pre-built wasm file.

Written by the indexing model from the issue text.