emacs: elgot and eldoc

- use eldoc-box (eldoc in child frame)
- make eldoc show docstrings for elisp
- setup eglot to auto enable
  - `prog-mode-hook` that checks current `major-mode` in `eglot-server-programs` and sees if `executable-find` give non-nil, and if so runs `eglot` (if it doesnt just work, `call-interactively`)?