Add new packages and build scripts for various libraries

- Added Nuklear GUI library with build script and configuration.
- Introduced OpenH264 encoder/decoder with build configuration.
- Added PortAudio library for audio I/O with custom build script.
- Included Python Execnet for multi-Python deployment.
- Added Pytest Xdist plugin for distributed testing.
- Introduced Shaderc for shader compilation tools.
- Added Snappy compression library with necessary patches and configuration.
- Included SoundTouch audio processing library with build configuration.
- Added SRT library for secure reliable transport.
- Introduced VapourSynth video processing framework with configuration.
- Added Vid.stab for video stabilization.
- Included WebRTC Audio Processing library with build configuration.
- Added X264 video encoding library with patches for POSIX compliance.
- Introduced X265 video encoder with build configuration.
- Added XKeyboard Config for X keyboard configuration files.
- Included Xorg XKBComp for keyboard description compilation.
- Added Xvidcore MPEG-4 video codec library with configuration.
- Introduced ZeroMQ messaging system with patches and build configuration.
- Added Zimg library for scaling and colorspace conversion.

extra/openh264/openh264.toml

@@ -0,0 +1,26 @@
+[build]
+type = "makefile"
+
+[build.flags]
+makefile_commands = ["make"]
+makefile_install_commands = ["make PREFIX='/usr' DESTDIR=$DESTDIR install-shared"]
+
+[dependencies]
+build = ["nasm"]
+runtime = [
+    "glibc",
+    "libunwind",
+    "libcxx",
+]
+
+[package]
+description = "H.264 encoder and decoder"
+homepage = "https://www.openh264.org/"
+license = "BSD-2-Clause"
+name = "openh264"
+version = "2.6.0"
+
+[[source]]
+extract_dir = "$name-$version"
+sha256 = "558544ad358283a7ab2930d69a9ceddf913f4a51ee9bf1bfb9e377322af81a69"
+url = "https://github.com/cisco/openh264/archive/v$version/$name-$version.tar.gz"