make sure compat is triggered in new jsx runtime

[Austaras]

preact relies on compat/render to be required/imported to generate compatible jsx object to react. This is generally enough, however as the current esm/cjs transistion, sometimes two copy of preact will exist in runtime for each kind of module. If compat is only imported once, everthing compat related would be broken.

This pr is not enough for compeletely fix this issue, but would make preact working when someone only import the new jsx function is imported. This is part of fix for gatsbyjs/gatsby#34783

[coveralls]

Coverage remained the same at 99.626% when pulling 7b5f114 on Austaras:master into 1b6fbc7 on preactjs:master.

[developit]

It might also be possible to ship this:

import { createElement, Fragment } from 'preact/compat';

function jsx(type, props, key, __source, __self) {
  const vnode = createElement(type, props);
  vnode.key = key;
  vnode.__source = __source;
  vnode.__self = __self;
  return vnode;
}

export { jsx, jsx as jsxs, jsx as jsxDEV, Fragment };

[marvinhagemeister]

@developit That's a neat idea! I'm leaning a little bit more to the approach chosen in this PR as using createElement inside jsx kinda defeats the purpose of using the new transform in the first place.

[marvinhagemeister]

@Austaras Thank you so much for making a PR for this 🎉