Prosody install guide needs improvement for 13.*

[SimJoSt]

Similar to #1234

In the last weeks, Prosody version 13.0.1 was released with a few breaking changes.
Lua 5.1 is not supported anymore, for example.

I've built luarocks for Lua 5.3, openssl 3.0 and libexpat on my own, to make the upgrade work, and was successful after many hours of trial and error. Too many details to remember to document them here, but here are some things I know for sure.
Custom builds of:

• libexpat
• openssl 3.0
• luarocks with Lua 5.3

.profile:

export PATH="$HOME/var/lib/luarocks/5.3/bin:$HOME/var/lib/prosody/app/bin:$HOME/var/lib/openssl/3.0/bin:$PATH"
export LD_LIBRARY_PATH="$HOME/var/lib/libexpat/lib:$HOME/var/lib/openssl/3.0/lib64:$LD_LIBRARY_PATH"
export PKG_CONFIG_PATH="$HOME/var/lib/libexpat/lib/pkgconfig:$HOME/var/lib/openssl/3.0/lib64/pkgconfig:$PKG_CONFIG_PATH"
export CFLAGS="-I$HOME/var/lib/libexpat/include -I$HOME/var/lib/openssl/3.0/include $CFLAGS"
export LDFLAGS="-L$HOME/var/lib/libexpat/lib -L$HOME/var/lib/openssl/3.0/lib64 $LDFLAGS"

eval "$(luarocks path)"

Building Prosody with custom paths and parameters:

$ ./configure --prefix=$HOME/var/lib/prosody/app \
  --lua-version=5.3 \
  --with-lua=/usr \
  --with-lua-include=/usr/include/lua-5.3

$ make \
  CFLAGS="-fPIC -I/home/simjost/var/lib/openssl/3.0/include -I/usr/include/lua-5.3 -I/usr/include" \
  LDFLAGS="-shared -L/home/simjost/var/lib/openssl/3.0/lib64 -L/usr/lib/x86_64-linux-gnu -llua-5.3 -lidn"

I am unreasonably hoping somebody more knowledgeable than me will try their hand and document the path to success.