Bump to version 0.2.0

[fitzgen]

Fixes #30

r? @pepyakin @DrGoldfire: Whoever wants to rubber stamp this :)

[DrGoldfire]

Thanks!

[fitzgen]

It looks like binaryen is failing:

+wasm-gc ../target/wasm32-unknown-unknown/release/wee_alloc_example.wasm ../target/wasm32-unknown-unknown/release/wee_alloc_example.gc.wasm
+wasm-opt -Oz ../target/wasm32-unknown-unknown/release/wee_alloc_example.gc.wasm -o ../target/wasm32-unknown-unknown/release/wee_alloc_example.gc.opt.wasm
[parse exception: index out of bounds: __rust_alloc]Fatal: error in parsing input

I don't know if this is a binaryen bug, or wasm-gc is creating bad input.

[pepyakin]

Complete guess, but maybe wasm gc mess up the name section? wasm2wat have —no-debug-names or similar option, i wonder if wasm opt have something like that

[fitzgen]

Working on the CI changes over in #32; will rebase on top of that and include that in the 0.2.0 release once the kinks are worked out.