title: Is there "includePath" option in clangd?
body: <p>I used to work with VSCode <a href="https://marketplace.visualstudio.com/items?itemName=ms-vscode.cpptools" rel="noreferrer">C/C++</a> extension. there was a feature in this extension(in a json file), called "includePath", which I could set the paths for my headers, so without execution of CMake or make, I would have the suggestion of my headers and code completion from those.</p>
  
  <p>now I have switched to neovim and clangd as the language server for code completion. I searched a lot to find the corresponding feature in clangd options but I could not find anything more than <a href="https://manpages.debian.org/experimental/clangd/clangd.1.en.html" rel="noreferrer">this link</a>.</p>
  
  <p>since the clangd is a powerful language server, I am in wonder if there is not such a feature in it. so I want to know is there actually such a feature in clangd? and if YES how can I use that?</p>
  
  <p>Note: I use a language client, called <a href="https://github.com/clangd/coc-clangd" rel="noreferrer">"coc-clangd"</a>. I don't know if it matters or not.</p>