Fixes #579 (Github Issue).

- 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.

Related to #554 (Github Pull Request).

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

Thanks Sorunome for setting up the automated build

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.

Related to https://github.com/vector-im/riot-web/pull/13914

Certain people organize their inventory in a different way
and we'd like to accommodate them.

Related to #542 (Github Issue).

Fixes #542 (Github Issues).

Fixes #539 (Github Issue).

Fixes #523 (Github Issue).

Besides /_synapse/admin, there are other things like
/_synapse/oidc, etc.

We should just proxy everything.

Fixes #534 (Github Issue).

There's no change in the source code. Just a release bump for packaing
reasons. It doesn't matter much for us here, but let's be on the latest
tag anyway.