Support wasm-pack backend

[titaneric]

This PR aims to solve #374 , which is the backend service for it.

Change of code

• Add new wasm-pack POST method which request Rust code and response with wasm_js, wasm_bg etc.
• New directory specific to wasm-pack
• Add cargo-pack which leverage wasm-pack to build the wasm code
• Add new Dockerfile for new channel rust-wasm-pack
• Add new Cargo.toml and dummy src/lib.rs for environment setting

Note

• Present supporting wasm library include the following

wasm-bindgen
web-sys
js-sys
wasm-bindgen-futures
yew
seed

• The above dependencies is defined in compiler/wasm-pack/Cargo.toml not top-crates/crate-modifications.toml, I am not sure which way is better.
• I have to cite seed-playground here who greatly influence me.

Demo

rust-playground

https://user-images.githubusercontent.com/12388235/114809686-39eb7e80-9ddd-11eb-96fd-a8b9e221e147.mp4

mdBook

https://user-images.githubusercontent.com/12388235/114810242-3b697680-9dde-11eb-85f3-a6e746aaa0c1.mp4

[titaneric]

Any news about this PR?

[lukechu10]

@shepmaster sorry for the ping but any chance this could be merged?

[titaneric]

@lukechu10 and anyone interested in this feature could try my own hosting rust-playground, and the repository is here.

Note that due to the limited budgets, I host it with the minimal resource (1 CPU and 1 G RAM). Hope that someone could try it and give me some feedback.

I will contine try to merge to original one.

[YJDoc2]

Hey, are there any updates on this from this repo owners? Is there any help needed for getting this forward, or this is supposed to be will-not-merge kind of thing?

[titaneric]

@YJDoc2, thank you for your interest. Obviously, the upstream is highly refactored after I submitted this PR. I will take care of the refactoring if exists any chance that could be merged into upsteam

[YJDoc2]

@shepmaster sorry for pinging, but would this project be interested in merging this/equivalent PR? This would be a pretty interesting feature to have in the playground.

[YJDoc2]

Hey @dtolnay @RalfJung sorry for the ping, but pinging you as you seem to also be one of the recent active contributors. It seems that @shepmaster might have missed the ping, or they might be busy with something else. Is there any chance of this getting merged after appropriate changes? Thank you!