A "dev" version of the REPL

[agriyakhetarpal]

• Figure out nightly wheel machinery
  • Investigate how to host both REPLs at the same time
  • Finalise where to host the nightly one
• Add a dropdown menu to switch between REPLs

Originally posted by @agriyakhetarpal in #26 (comment)

[agriyakhetarpal]

CORS headers are now being shipped with Anaconda.org (xref pyodide/pyodide#4898). I've opened and will be working on jupyterlite/pyodide-kernel#166 soon to make this task easier to accomplish.