[ENHANCEMENT] Create a new generated npm workspace for typescript ANTLR generated code

**Is your feature request related to a problem? Please describe.**
We eventually want to support performing client side validation of search and provide suggestions depending on the term (via a custom visitor). But before that, we need to actually generate the ANTLRv4 code for typescript. This issue covers that.

**Describe the solution you'd like**
- A new npm workspace in [package.json](https://github.com/GoogleChrome/webstatus.dev/blob/40ea43829c9104a548db5097c0bc137aa67b8e3c/package.json#L12) for the antlr code. Named `lib/gen/antlrv4/ts-antlrv4`.
- Update the gitignore to ignore the directory (should not be needed though because of this [rule](https://github.com/GoogleChrome/webstatus.dev/blob/40ea43829c9104a548db5097c0bc137aa67b8e3c/.gitignore#L45))
- Update the antlr-gen Makefile [target](https://github.com/GoogleChrome/webstatus.dev/blob/40ea43829c9104a548db5097c0bc137aa67b8e3c/Makefile#L237-L238) to also call the typescript [target](https://github.com/antlr/antlr4/blob/master/doc/typescript-target.md)
- Add any other needed files to make the new workspace valid. (Probably just a package.json [like the other typescript generated workspace](https://github.com/GoogleChrome/webstatus.dev/blob/main/lib/gen/openapi/ts-webstatus.dev-backend-types/package.json))