Fixed repository link for mx-puppet-steam

- https://github.com/icewind1991/mx-puppet-steam is the link that's referenced by the documentation.
- The previous link, https://github.com/matrix-steam/mx-puppet-steam, is invalid/inaccessible to the public.

Fixed Steam link

Run all API self checks in check_mode

swap links

Expose reCAPTCHA variables and document

Related to #554 (Github Pull Request).

Related to #557 (Github Pull Request).

Add mx-puppet-steam

Upgrade Synapse (1.15.1 -> 1.15.2)

Related to #540 (Github Pull Request).

Add mx-puppet-discord

https://github.com/matrix-discord/mx-puppet-discord/issues/80

Thanks Sorunome for setting up the automated build

Related to #551 and #555 (Github Pull Requests).

Add mx-puppet-twitter

Add mx-puppet-instagram

4.5.1.3 fixes a security vulnerability:
https://github.com/coturn/coturn/security/advisories/GHSA-c8r8-8vp5-6gcm

Signed-off-by: Tulir Asokan <tulir@maunium.net>

`matrix_container_images_self_build` was not really doing anything
anymore. It previously was influencing `matrix_*_self_build` variables,
but it's no longer the case since some time ago.

Individual `matrix_*_self_build` variables are still available.
People that would like to toggle self-building for a specific component
ought to use those.

These variables are also controlled automatically (via
`group_vars/matrix_servers`) depending on `matrix_architecture`.

In other words, self-building is being done automatically for
all components when they don't have a prebuilt image for the specified
architecture. Some components only support `amd64`, while others also
have images for other architectures.

ma1sd 2.4.0 announced experimental support for arm64.
We're making use of those arm64 images instead of self-building.

Update Jitsi to stable-4627-1

Ma1sd v2.4.0

Documentation of the variables added in the PR #548