Remove or replace wee_alloc from documentation

[bcheidemann]

🐛 Bug description

It seems as though wee_alloc is no longer maintained but it is recommended in the wasm-pack documentation.

See:

• Is this repo still maintained? wee_alloc#107
• https://rustsec.org/advisories/RUSTSEC-2022-0054.html

🤔 Expected Behavior

1. lol_alloc should be recommended over wee_alloc
2. The documentation should inform readers that wee_alloc is no longer maintained and encourage them to use lol_alloc instead

👟 Steps to reproduce

1. Visit https://rustwasm.github.io/docs/wasm-pack/tutorials/npm-browser-packages/template-deep-dive/wee_alloc.html

🌍 Your environment

Include the relevant details of your environment.
wasm-pack version: latest
rustc version: n/a