Missing documentation on refactoring & completion

[wusatosi]

Currently, only rename is mentioned under the features tab.

Should we include other implemented refactoring features like inline/ extract variables? Related: https://github.com/clangd/clangd/issues/446#issuecomment-653759209

Besides inline/ extract variables, refactoring functionalities under clangd/refactor/tweaks is barely documented.

Is this intended?