Other than reformatting documentation for Open Collective, this
commit also moves it to the "Financial" category from "Communications".
This is because Open Collective is mainly a fundrising + legal status +
money management platform, as stated in https://opencollective.com/.
Part of #29592.
Note: This doesn't change the occurences in the Zapier integration doc,
since they refer to pieces of the UI in Zapier, which may still be using
the "Stream" terminology.
markdown-include is GPL licensed.
Also, rewrite it as a block processor, so that it works correctly
inside indented blocks.
Signed-off-by: Anders Kaseorg <anders@zulip.com>
PieterCK
Mateusz Mandera
Tim Abbott
Anders Kaseorg
Lefteris Kyriazanos