New picker command to open file picker at LSP root of current buffer

I routinely open helix in base directory with several related repos, I can open a picker in the current buffer dir with space-F and a picker over all the repos with space-f but it would be handy to open one in the current buffer's repository as a whole. Neovim provides this feature and I believe it is based on the directory the LSP reports as the buffer's root dir.
