Animate torconnect's progress bar

It's a known issue that bootstrapping can progress very slowly for users with low bandwidth, or censored users using slower bridges (e.g. Snowflake). The current front-end experience can result in the progress bar appearing completely static for periods of time as Tor Browser attempts to complete a certain bootstrapping step, and users sometimes misinterpret this as bootstrapping having frozen entirely.

Usually that's not the case, and Tor Browser is still attempting to connect. To communicate its working state better, I'd like to explore adding an additional layer of animation to the loading bar similar to this:

I've mocked up an example, although I can't animate both layers simultaneously – so you'll just have to imagine it's moving from left to right in addition to transitioning through the gradient:

• Light theme
• Dark theme

This particular example is essentially a 2000px wide gradient from #FC00FF → #00DBDE → #FC00FF on a 1500ms loop.