Webpack requires fullyResolved for .mjs files to bundle properly

[jacob-alford]

This is an issue that also effects schemata-ts. Essentially, .mjs files need to specify the file extension when importing from non-mjs files. This issue arises because kuvio's exports import from fp-ts/Foo where they need to be replaced with fp-ts/es6/Foo.js for .mjs files. It might also be good to replace .js fp-ts imports with fp-ts/lib/Foo.js too.

Source of issues: all .mjs files which import from fp-ts/Foo
Example: https://unpkg.com/browse/kuvio@1.3.1/dist/index.mjs