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 modifies the doc.md to:
* Use consistent language and style.
* Use the number 1 for all numbered steps and let Markdown take
care of the rest.
* Have detailed steps on how to get to the Integrations settings
instead of just linking to the page.
* Remove unnecessary screenshots.
Anders Kaseorg
Eeshan Garg