Meta: Add gn rules for dependencies of LibWeb

There's a lot of them, and LibWeb is a massive set of files to build as
well, so let's add these first :^).

Meta/gn/secondary/Userland/Libraries/LibVideo/BUILD.gn

@@ -0,0 +1,27 @@
+shared_library("LibVideo") {
+  output_name = "video"
+  include_dirs = [ "//Userland/Libraries" ]
+
+  deps = [
+    "//AK",
+    "//Userland/Libraries/LibAudio",
+    "//Userland/Libraries/LibCore",
+    "//Userland/Libraries/LibGfx",
+    "//Userland/Libraries/LibIPC",
+    "//Userland/Libraries/LibThreading",
+  ]
+  sources = [
+    "Color/ColorConverter.cpp",
+    "Color/ColorPrimaries.cpp",
+    "Color/TransferCharacteristics.cpp",
+    "Containers/Matroska/MatroskaDemuxer.cpp",
+    "Containers/Matroska/Reader.cpp",
+    "PlaybackManager.cpp",
+    "VP9/Decoder.cpp",
+    "VP9/Parser.cpp",
+    "VP9/ProbabilityTables.cpp",
+    "VP9/SyntaxElementCounter.cpp",
+    "VP9/TreeParser.cpp",
+    "VideoFrame.cpp",
+  ]
+}