Add support for import `.mjs` file

[NNBnh]

As the name suggested. I and other need this to work with Gleam gen code. Thanks

[chucksellick]

I was able to import an mjs file just by setting "allowJs": true in my compilerOptions in tsconfig

[NNBnh]

It's somehow still can't import on Godot side T_T, but I found the workaround of compile all Gleam build result with bun and rename all the file to ts...