Update CONTRIBUTING.md

* `Alien::raylib` downloads raylib, builds it and installs it in the Perl module path (Basically abusing CPAN as package manager)
* `Graphics::Raylib::XS` depends on `Alien::raylib` and reexports all C symbols as XS symbols usable in Perl
* `Graphics::Raylib` depends on `Graphics::Raylib::XS` and is the actual Perl wrapper with a Perlish API, which users should be using

Contributors added to contributing file

Reviewing GetTime() functionality

Some programs like tools could not require audio support

Develop

Build shared libs, games and examples on CI

Now with external OpenAL and GLFW dependencies removed,
we don't have to worry about installing them in CI.
Shared libraries are now always built along with static libs.
Games and examples are built everwhere except for Visual Studio,
because Physac needs pthreads, which VS doesn't provide.

If shader file could not be found on loading it crashed, instead added
fallback to default shader!

Let the user choose if using rres external library

Add library versioning to Make/CMake build systems

Less maintenance overhead that way,
given that make/CMake now also do library versioning.

See #401 for the discussion.
Also bumps version number to 1.9.2 without the -dev,
because neither ELF nor MachO like such a suffix.
The -dev suffix will have to be restricted to the git tags.

Updated to latest GLFW library and working on Wayland support, still
looking how to implement it on raylib because it just exposes
PLATFORM_DESKTOP and defaults to X11 windowing system on Linux...

OpenAL Soft backend is still available in audio module, I'm thinking if
exposing it for building in some way or just left it there for advance
users to switch to it manually in case of necessity...

Added dr_wav for a future use

mini_al integration

Updated raylib version to 1.9-dev for development pourposes.

Next raylib version is planned to implement a big amount of changes, so
the version bump.

Added support compilation with cmake for FreeBSD