Setup include path in vscode with clangd

[aben20807]

Ref: https://stackoverflow.com/questions/61206703/is-there-includepath-option-in-clangd#comment126291138_69269142

1. Add .clangd in the root of repo with contents:

CompileFlags: # Tweak the parse settings
Add: 
  - "--include-directory=/path/to/include/"
  - "--include-directory=/anothor/path/to/include/"

2. Add config in .vscode/settings.json ({} is the outer one)

{
  "clangd.fallbackFlags": [
      "--enable-config",
  ]
}