Improve build time

Also, various other changes:

• Add run script that:
  1. Checks for deno/mustache prerequisites.
  2. Prompts user for username and token.
  3. Handles all the build logic.
  4. Automatically opens the built HTML in your browser.
  5. Does not rebuild unless you delete the existing HTML file.
• Refactored fetch script to:
  1. Use a fancy ✨AsyncGenerator✨!
  2. Rely on GitLab's rate limit headers/status codes to more quickly fetch user event pages, and back off when we exceed the rate limit (although in practice this will never happen, since GitLab.com currently allows 2000 requests per minute to the user events endpoint. The endpoint simply doesn't respond quickly enough, given we request pages in series, for us to ever exceed our quota).
  3. Wait for writes to standard out, to ensure complete writes so as to avoid a broken output JSON file.
  4. Make standard error logging less verbose.
  5. Exit with error status if main() throws.
• Added the s (dotAll) and i (ignoreCase) RegExp flags to filters for better search results.