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/ell/ell.toml

@@ -0,0 +1,27 @@
+[build]
+type = "autotools"
+
+[build.flags]
+skip_tests = true # flaky
+
+[dependencies]
+runtime = [
+    "libunwind",
+    "glibc",
+]
+test = [
+    "dbus",
+    "procps-ng",
+]
+
+[package]
+description = "Embedded Linux library"
+homepage = "https://git.kernel.org/pub/scm/libs/ell/ell.git/"
+license = "LGPL-2.1-or-later"
+name = "ell"
+version = "0.83"
+
+[[source]]
+extract_dir = "$name-$version"
+sha256 = "39a562f5ab2768e69da1ffbb1f98a8eb3483baffc7d2ef6adc3705e4fd4e53fb"
+url = "https://mirrors.edge.kernel.org/pub/linux/libs/$name/$name-$version.tar.xz"