feat: switch prettier-plugin-glsl output to ESM

[NaridaL]

Fixes #44

Problem

When prettier-plugin-glsl (CJS) is loaded alongside another ESM plugin that also imports chevrotain (e.g. prettier-plugin-wgsl), Node throws:

Cannot require() ES Module .../chevrotain/lib/src/api.js because it is not yet fully loaded.
This may be caused by a race condition if the module is simultaneously dynamically import()-ed via Promise.all().

This happens because Prettier loads all plugins concurrently via Promise.all, and chevrotain v12+ is ESM-only. When one plugin import()s chevrotain and another require()s it simultaneously, Node hits a race condition.

Solution

Switch the rollup output format from CommonJS to ESM:

• rollup.config.mjs: format: "commonjs" → format: "es"
• package.json: "type": "module", exports path updated to .es.js
• babel.config.js → babel.config.cjs (uses module.exports)
• jest.config.js → jest.config.cjs (uses module.exports)
• tsconfig.json: updated include for renamed babel config

This is safe for all current Node LTS versions — ESM has been stable (unflagged) since Node 14+, and the package already requires >=22.0.0. Prettier 3.x natively supports ESM plugins.

Testing

• All existing tests pass (59 passed, 9 skipped)
• Added an integration test (test-esm-compat/) that reproduces the exact issue scenario: loading prettier-plugin-glsl alongside a fake ESM chevrotain-based plugin via Promise.all, then formatting a GLSL file. This passes cleanly with the ESM output.