* Change Caddy links

Current links points to Caddy v1 which is deprecated.

Signed-off-by: Nicolai Søborg <git@xn--sb-lka.org>

Just in case people head straight to the troubleshooting section and find themselves at a dead end.

Continuation of #7379

Adds a section in the README telling people to go to #synapse:matrix.org instead of using github issues. I'm not entirely sure about placing it above the install section but then people are likely to first seek support when installing (if something goes boom), and it's probably better to have it as high as possible anyway so people actually see it.

This PR moves the "support is in #synapse:matrix.org" in the bug report template outside of the comment as some people seem to ignore what's in the comments, and phrase it a bit more like the support request template. It also adds a default issue template that says the same thing. It's also adding a notice about the security disclosure to both the default template and the bug report one.

It also adds a badge to the top of the README with an alt text saying about the same message if the badge doesn't load (e.g. if matrix.org is slow).

Fixes #6826 

s/reverse_proxy.rst/reverse_proxy.md/

s/reverse_proxy.rst/reverse_proxy.md/

Converting some of the rst documentation to markdown.  Attempted to
preserve whitespace and line breaks to minimize cosmetic change.

Signed-off-by: Benjamin Saunders <ben.e.saunders@gmail.com>

Improved federation configuration docs.  Specifically detailing  .well-known and SRV based delegation methods. 

Inspiration Valentin Lab <valentin.lab@kalysto.org> for https://github.com/matrix-org/synapse/pull/4781

* add trivial clarification about jemalloc

* switch from google.com to recaptcha.net

because https://developers.google.com/recaptcha/docs/faq#can-i-use-recaptcha-globally

Lots of updates to the README/INSTALL.md.

Fixes #4601.

Factor out the reverse proxy info to a separate file, add some more info on
reverse-proxying the federation port.

The readme was getting pretty unmanageable and hard to grok. This is an attempt to simplify things by moving installation instructions from the README to a separate file. I've tried to resist the temptation to fix too much stuff while I'm here - it mostly just copies-and-pastes from one doc to the other, and changes from rst to md syntax.

Co-Authored-By: anoadragon453 <1342360+anoadragon453@users.noreply.github.com>

Co-Authored-By: anoadragon453 <1342360+anoadragon453@users.noreply.github.com>

* update debian installation instructions

* docs PR is docs

* remove dh_params and set better cipher string

* Update README to not lie about required restart

Signed-off-by: Aaron Raimist <aaron@raim.ist>

* Add changelog

Signed-off-by: Aaron Raimist <aaron@raim.ist>