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 make build output, including JSX compilation, compatible with Node.js ES Module format. lume#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.
• @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.