fix: add explicit TypeScript parser to prevent XML plugin conflicts

[elliottcarlson]

Problem

The @prettier/plugin-xml plugin in Prettier 3.6.0+ incorrectly identifies TypeScript files as XML, causing parsing errors during the post-install formatting step.

Error details:

• Errors are emitted during the npx prettier --write post-install step.
• Files affected: scripts/lint.ts, src/bundleEntry.ts, src/main.ts
• Error: `SyntaxError: Expecting token of type --> OPEN <-- but found --> ...
• Root cause: XML plugin attempting to parse TypeScript files

Solution

Add explicit TypeScript parser configuration in prettier.config.mjs overrides to ensure .ts files are correctly identified and parsed.

Testing

• ✅ npx isaacscript@latest init completes successfully
• ✅ Post-install npx prettier --write runs without errors
• ✅ All TypeScript files format correctly
• ✅ XML formatting remains unaffected

Impact

Fixes broken initialization flow for new projects using the latest Prettier version while maintaining compatibility with all existing plugins.

[Zamiell]

thank you!