Compile the tendermint and light-client crates to WASM

[romac]

See: #463

This PR also adds a job to the CI to test that both crates can compile to WASM.

• Referenced an issue explaining the need for the change
• Updated all relevant documentation in docs
• Updated all code comments where relevant
• Wrote tests
• Updated CHANGELOG.md

[romac]

I had to disable the only previously enabled acceptance test of the light node CLI for the test suite to pass (7c07134). Without this commit, cargo test --all-features --no-fail-fast would fail with:

       Doc-tests tendermint-light-client
    error[E0460]: found possibly newer version of crate `tendermint` which `tendermint_rpc` depends on
     --> /Users/coromac/Informal/Code/Current/tendermint-rs/light-client/src/components/io.rs:7:5
      |
    7 | use tendermint_rpc as rpc;
      |     ^^^^^^^^^^^^^^
      |
      = note: perhaps that crate needs to be recompiled?
      = note: the following crate versions were found:
              crate `tendermint`: /Users/coromac/Informal/Code/Current/tendermint-rs/target/debug/deps/libtendermint.rlib
              crate `tendermint`: /Users/coromac/Informal/Code/Current/tendermint-rs/target/debug/deps/libtendermint-735716e8d731096d.rmeta
              crate `tendermint_rpc`: /Users/coromac/Informal/Code/Current/tendermint-rs/target/debug/deps/libtendermint_rpc-ad41c355acf2752f.rlib

    error: aborting due to previous error

It is currently unclear why this error has appeared, though I suspect it is a bug in Cargo related to features flags (which we now use to disable non WASM-compatible code).

EDIT: The reason for why disabling this test resolves the issue above, is that there is no more a need to rebuild the light node crate to run the light node binary with cargo run. It's not clear why rebuilding the crate is necessary when running cargo run as part of the test (when everything should have been compiled already, though perhaps not with the same flags) but I suspect that doing so in the middle of running (doc)tests is causing the issue.

[romac]

Since the test I had to comment out was just testing that the version number emitted by the light-node CLI was correct, I feel like this should not be a blocker to merge this PR, though we will at some point need to figure out how to fix the issue anyhow (or just hope that a Cargo update will resolve it, might open an issue on the Rust bugtracker or post on /r/rust in the meantime).

[romac]

[liamsi]

Wohoooo 🎉

[melekes]

👍

[brapse]

Love this 👍

[brapse]

👍