Support registering custom file extensions

[dukeofsussex]

When this library still used require-all, it was possible to load TS files during dev with

.registerCommandsIn({
  filter: /^([^.].*)\.(?:js|ts)$/,
  dirname: join(__dirname, 'commands'),
})

This is no longer possible since 5.x, so this PR aims at supporting it out-of-the-box.

[Snazzah]

I'm pretty sure just enabling this outright may create a bunch of errors, could this be an argument to enable instead?

[dukeofsussex]

I'm interested as to why or how it would cause issues, but I can gladly change it to something like

  registerCommandsIn(commandPath: string, endings: string[] = ['.js', '.cjs'])

[fangmarks]

I'm interested as to why or how it would cause issues, but I can gladly change it to something like

I'm pretty sure Typescript generates .d.ts files when you set "declaration": true in your tsconfig.json, which would then cause slash-create to load those files and cause various issues.

Personally I like the option you posted, though I'd make passing endings optional xP

[dukeofsussex]

I'm pretty sure Typescript generates .d.ts files when you set "declaration": true in your tsconfig.json, which would then cause slash-create to load those files and cause various issues.

Good point, hadn't thought of the declaration files. Also the proposed solution already makes passing endings optional, but maybe it should be changed to an optional additionalEndings instead.

[Snazzah]

Good point, hadn't thought of the declaration files. Also the proposed solution already makes passing endings optional, but maybe it should be changed to an optional additionalEndings instead.

Yeah, this is alright.