Adding a Issue and PR template for the project, as well as adding cross-env for cross platform dev support.

[Lofty-Brambles]

The topic is pretty much self-explanatory. I'm not sure as to what or how the issue/PR templates are going to be, and the cross-env should be a simple npm i cross-env -D.

[lyqht]

1 possible issue of introducing cross-env is to make sure that it still works in a GitPod environment. I have tried GitPod in another project and they used the library, but the shell will say that

sh: 1: cross-env: not found

Not too sure how this can be resolved!

[Lofty-Brambles]

$ pnpm i
$ pnpm i cross-env
$ pnpm run dev

seems to be working.

[lyqht]

great! for the issue/PR templates, I'm not too sure what are the better template references out there as well. feel free to propose any that you think fits this project!