Add keybinding to swiching between source and header files

[Aukstkalnis]

Is your feature request related to a problem? Please describe.

I am trying Lapce for C development and started to miss VSCoce feature to easily switch between header and source files with Alt+o keybinding. This is helpful feature. I think clangd has this feature but I am not sure.

Describe the solution you'd like

So the feature should work as in VSCode. Alt+o opens header file with the same name as current source file. Pressing Alt+o again will jump back to source file. The header file can be in different folder then source file. The feature should work with C++ as well.