wasm solve

[martinjrobins]

Add a wasm solver to the project. This will allow the project to be used in a browser.

[martinjrobins]

See Chris00/sundials-sys#1 for issue building sundials to wasm
See also:

• Status of rust+C bindings for wasm targets rustwasm/team#291
• Document wasm-bindgen incompatibility with C/C++ rustwasm/wasm-bindgen#2209

[martinjrobins]

solver is being moved to https://github.com/martinjrobins/diffsol