Support .wast extention for --textFile

[MaxGraey]

this add ability print .wast (superset text format) as well.

@dcodeIO Sometimes this preferable. Especially useful for producing binaryen's test cases.

This shouldn't break any backward compatibility.

• I've read the contributing guidelines

[dcodeIO]

Note that Binaryen's .wast format isn't strictly a superset because it represents some instructions in non-standard ways, for example by having tuple.make etc. instructions that only map to Wasm text format after postprocessing, or explicit pops. As such I worry that this might become confusing if folks are using .wast still, expecting the output to be valid, and never switched to .wat, but I agree that providing a way to emit Binaryen's format is nice to have. Perhaps --binaryenFile?

Also I'm not sure if .wast is already reserved for Wasm test cases with assert_return instructions etc.?

[MaxGraey]

Note that Binaryen's .wast format isn't strictly a superset because it represents some instructions in non-standard ways

I know. That's why it still use by default.

Also I'm not sure if .wast is already reserved for Wasm test cases with assert_return instructions etc.?

I don't think so. But one of main goals of this changes is producing text fixtures for binaryen's test files as well

[MaxGraey]

I worry that this might become confusing if folks are using .wast still, expecting the output to be valid, and never switched to .wat, but I agree that providing a way to emit Binaryen's format is nice to have. Perhaps --binaryenFile?

If somebody still use .wast but expect .wat I guess it has pretty old AS and when it update perhaps just ask here what was changed? --binaryenFile isn't clear. Also we already have a lot of keys binaryFile, jsFile, textFile, dtsFile and etc.