export node module as .mjs file

[jaeh]

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• [?] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

this outputs an mjs file instead of a js file to node/module.mjs

@magic/core is using node 14.2.0 and mjs files without compilation, and, contrary to most build tools, nodejs is not capable to detect modules automagically when importing.

alternatively to this commit we could also set "type": "module", in package.json, but i would expect that to break some commonjs applications on older node versions.

please note: i do not have a commonjs application ready to test this in!

> @magic/[email protected] build /media/j/data/dev/magic/core
> NODE_ENV=production src/bin.mjs build

/media/j/data/dev/magic/core/node_modules/hyperapp-render/node/module.js:3
import { Readable } from 'stream';
^^^^^^

SyntaxError: Cannot use import statement outside a module
...

[codecov-commenter]

Codecov Report

Merging #19 into master will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##            master       #19   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            2         2           
  Lines          127       127           
  Branches        35        35           
=========================================
  Hits           127       127           

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[frenzzy]

Thank you for the PR!
As far as I know not all the tools support .mjs extension yet.
I have another solution here: #20

[frenzzy]

Just released v3.4.0 with the fix. Thanks again!

[jaeh]

@magic/core 0.0.76 is using 3.4.0 now,
only needed change was
import render from 'hyperapp-render'
to
import * as render from 'hyperapp-render'

thank you so much for all the work!