proto-loader: Fix yargs types & update README

[badsyntax]

There seems to have been a type update via patch version in @types/yargs where argv._ is now defined as _: Array<string | number>;, see:

https://github.com/DefinitelyTyped/DefinitelyTyped/blob/6de1fd533383aa8fcac9460edd2ee5d36989fa7b/types/yargs/index.d.ts#L643

This is why we need to do argv._ as string[] as well as add parse-positional-numbers: false parser config to prevent yargs from parsing positional args to numbers. I need to use @ts-ignore because the types for yargs-parser need updating, see: DefinitelyTyped/DefinitelyTyped#50196

I noticed this as a did a clean clone of this repo follow by a npm install and the compile script failed to build.

I also added example usage to the README as I believe this will help with understanding how to use the generator.

[badsyntax]

@murgatroid99 this is now good for a review.

[murgatroid99]

Git sees this as conflicting with the previous PR you sent, so can you resolve that? Also, did you intend to update all of those dependencies? I'm uncertain about the major version bumps to gts and especiallly typescript.

[badsyntax]

I've simplified the changes.

Not sure why I bumbed gts and typescript but i've reverted those changes.

And there's no need to bumb any yargs package versions because the type fixes for yargs-parser are "automatically" pulled in due to the usage of the star (*) version number defined in the @types/yargs package:

I'm sorry for force pushing, but it was easier this way due to the conflicts.