upgrade to new web component standards

[keithamus]

Much like github/auto-complete-element#104, github/auto-check-element#62, and github/clipboard-copy-element#67, this PR upgrades us to the latest idioms we have within the Custom Elements landscape at GitHub. This means:

Development changes:

• Update CI to use Node 18 LTS
• Uses web-test-runner over karma.
• Uses a slightly improved eslint config
• Minor changes to TSconfig
• Uses esbuild over rollup

User faces changes:

• Emits JSX types, making it compatible with React
• Reworks exports allowing for various patterns, including importing the web component without defining, or defining under different scopes or registries.
• Outputs a custom elements manifest.

These changes make it easier for us to integrate into various systems, without causing breakages in older systems.

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