support aarch64

[jasonbeach]

Currently on x86, if clangd is not installed, the extension will ask if it can automatically be installed. On an aarch64 platform it simply sends you to the clangd homepage that has instructions to install. Those instructions are essentially to apt install clangd from disto package managers, which unfortunately at least on 18.04 has a really old version (clangd 10). I'm not sure where the extension downloads the x86 version from, but was wondering if it also has a aarch64 version. On LLVM's release page (https://github.com/llvm/llvm-project/releases/tag/llvmorg-14.0.0 for instance) there is an aarch64 version of the entire LLVM package....which is obviously overkill for just downloading clangd itself, but I don't see a download of just clangd.

[HighCommander4]

Depends on https://github.com/clangd/clangd/issues/1261