Add missing includes to type.h (#1491)
Add missing includes to type.h (#1491)

- cassert for assert
- confing.h for WABT_UNREACHABLE

I think it was working because type.h was only included in common.h,
both cassert and config.h was included prior to including type.h.
WebAssembly/wabt,WebAssembly/sexpr-wasm-prototype,WebAssembly/sexpr-wasm-prototype,WebAssembly/wabt,WebAssembly/sexpr-wasm-prototype,WebAssembly/sexpr-wasm-prototype,WebAssembly/sexpr-wasm-prototype,WebAssembly/wabt,WebAssembly/wabt,WebAssembly/sexpr-wasm-prototype,WebAssembly/wabt