Improved lsp-completion--get-documentation option

[nice]

Is your feature related or already mentioned on the wishlist?
Mentioned briefly in the second point of : #2892 (comment)

First of all, thanks to all the contributors of lsp-mode.

Feature request:
Option to include/prefix lsp:completion-item-detail text to lsp:completion-item-documentation?.
It currently clutters the completion popup, especially with typescript language server.
I have added an advice to merge the detail and the documentation, which solves the problem for me, but would be good to have this as a configuration if possible.

Please refer to before and after screenshots below:

Before

(setq lsp-completion-show-detail t)
(company-posframe-mode 1)

After

(setq lsp-completion-show-detail nil)
(company-posframe-mode 1)

(defun improved-completion-quick-help (orig item &rest args)
  (let ((doc (apply orig item args))
        (detail
         (-some->> item
           (get-text-property 0 'lsp-completion-item)
           (lsp:completion-item-detail?)))
        )
    (concat "\n" detail "\n\n" doc)))
  
(advice-add 'lsp-completion--get-documentation :around #'improved-completion-quick-help)

[yyoncho]

I don't mind having this as an option with vscode behavior being the default.

[ericdallo]

Looks good to me!
I'd prefer using this feature as well

[mpereira]

This is great, thanks @nice!