feat(other): migrate to redocly-cli v2

[h0pped]

What/Why/How?

Migrates the action to @redocly/cli v2, which is published as a pure ESM module.

• Bump @redocly/cli 1.34.13 → 2.31.2 and add @redocly/openapi-core 2.31.2 as a direct dep (used for loadConfig).
• Switch the action to ESM: "type": "module" in package.json, module: ESNext / moduleResolution: bundler in tsconfig.json, Node >=20.19.0.
• Replace ncc with an esbuild bundler script (scripts/build.mjs) that emits an ESM dist/index.js.
• Includes a small esbuild plugin that shims @redocly/cli's internal utils/package.js by reading name / version / engines from the installed @redocly/cli/package.json at build time, so the bundled CLI reports the correct version
• Defer-load the CLI (src/redocly-cli.ts, src/redocly-config.ts): the CJS Jest runner can't statically import the pure-ESM CLI (ERR_REQUIRE_ESM), so handlePush / handlePushStatus / loadConfig are now dynamically imported at call time.
• Update ESLint plugins and Jest config for the ESM setup; refresh tests for the new dynamic-import flow.

Reference

Testing

• npm run all (prettier, lint, unit tests, package).
• Smoke tests pass against the rebuilt dist/index.js.
• Tested by performing cicd push via gh action on that branch

Screenshots / Video (optional)

Additional context