Broken infoview in Gitpod with 0.0.70+

[Kha]

Starting with version 0.0.69, the infoview is empty on gitpod.io, presumably due to this error in the console:

Uncaught TypeError: Error resolving module specifier “@lean4/infoview”. Relative module specifiers must start with “./”, “../” or “/”.

Example: https://gitpod.io/#https://github.com/Kha/tba-2022

[gebner]

I guess this is due to #151.

cc @Vtec234

[Vtec234]

Ahhhh, it's because only Chromium supports importmaps. By the way, this only appears in 0.0.70+ - 0.0.69 should still work. To fix this, we will probably need to polyfill them using SystemJS.