Add support for Solid JSX

[trusktr]

The tests and global build for a package with .tsx outputting to .jsx currently don't work because lume/cli's Webpack setup isn't configured to consume .jsx yet.

[trusktr]

Karma-webpack is now configured to consume .jsx files, but the top-level files that run through karma (i.e. *.test.js files) can not have .jsx extensions, otherwise Karma will fail to pass those files to karma-webpack for handling. We've gotten rid of Karma, replaced it with @web/test-runner. It consumes plain .js files, and we transpile .tsx to .js.

• [ ] make lume build output everything as .js with JSX compiled away (we need to do this in order to be ES Module compliant anyway, more details in https://github.com/lume/lume/issues/219)
  • We had implemented this at one point, but the recent cli updates are outputting .jsx files again. We'll need to use both TypeScript and a secondary Babel step.
• [x] @lume/element does not depend on itself, so when we run tests in the lume/element repo, the JSX build output's @lume/element import specifiers need to be replaced with something else or else lume/element tests don't know how to import the library they're in. This is a bit meta. For the lume/element case, maybe the webpack config for karma-webpack can have a resolve.alias setting to make @lume/element alias to dist/index.js No longer relevant, tests work great in @web/test-runner.