Added Double Precision documentation. #631

Job	Run time
🍏 MacOS (universal, editor)	1m 7s
🐧 Linux (x86_64, editor)	50s
🍏 MacOS (universal, template_release)	1m 16s
🐧 Linux (x86_64, template_release)	55s
🍏 Ios (universal, template_debug)	58s
🏁 Windows (x86_64, editor)	3m 12s
🍏 Ios (universal, template_release)	1m 35s
🏁 Windows (x86_64, template_release)	3m 17s
🤖 Android (arm32, template_debug)	30s
🕸 Web (wasm32, template_debug, yes)	28s
🕸 Web (wasm32, template_debug, no)	42s
🤖 Android (arm32, template_release)	42s
🕸 Web (wasm32, template_release, yes)	43s
🤖 Android (arm64, template_debug)	33s
🕸 Web (wasm32, template_release, no)	54s
🤖 Android (arm64, template_release)	36s
🤖 Android (x86_32, template_debug)	46s
🤖 Android (x86_32, template_release)	31s
🤖 Android (x86_64, template_debug)	39s
🤖 Android (x86_64, template_release)	29s
📦 Collect GDExtension binaries	11s
🧪 Testing API: ubuntu-20.04, Godot-stable_linux.x86_64.zip	13s
🧪 Testing API: macos-latest, Godot-stable_macos.universal.zip	42s
🧪 Testing API: windows-latest, Godot-stable_win64.exe.zip	35s
	22m 24s

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