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>
This commit:
* Adds a missing step to the documentation.
* Replaces wording such as "Go to X" with "Click on X".
* Removes the unnecessary screenshots.
* Rearranges the doc to contain only 4 steps. For uncomplicated
setups, 4 seems to be the right number.