Update Project Templates documentation

[stefan-pdx]

Hello,

Currently the Project Templates documentation links to rustwasm/rust_wasm_template which has been deprecated in favor of rustwasm/wasm-pack-template or rustwasm/rust-webpack-template.

It'd be nice to update the documentation here to reflect that.

Cheers!

[fitzgen]

These goals documents are all probably a little out of date now. And a bunch of them never got filled out... Unsure if it is worth maintaining these long term or just scrapping them :-/

[fitzgen]

(Thanks for filing the issue, though!)