Narrow TypeScript spec exclusions to spec directory

[aduth]

🛠 Summary of changes

Limits TypeScript exclusions for spec files to those in the spec/ directory.

Why?

• Moves in the direction of full type-checking coverage
• Recent conventions prefer adding spec files in app/javascript, so...
  • ... spec/ files should be considered "legacy"
  • ... we want to enforce full type checking coverage for new spec files in app/javascript
• Helps identify legitimate issues (e.g. see included changes)

📜 Testing Plan

Verify that TypeScript type-checking passes:

yarn typecheck

[zachmargolis]

does marking it as optional like this work here?

Suggested change

	* @param {undefined|Record<string, any>} object
	* @param {Record<string, any>=} object

[aduth]

It looks like TypeScript would treat that as an optional parameter and then get mad about a required parameter following an optional parameter.

app/javascript/packages/rails-i18n-webpack-plugin/rails-i18n-webpack-plugin.js:35:22 - error TS1016: A required parameter cannot follow an optional parameter.

35 function dig(object, keyPath) {
                        ~~~~~~~