consult-denote for GNU Emacs

Integrate the denote and consult packages:

• Denote : A file-naming scheme to easily retrieve files of any type. Useful for note-taking and long-term storage files.
• Consult: Enhanced interactivity for the standard Emacs minibuffer, such as a preview mechanism for buffers and an asynchronous grep/find.

The purpose of consult-denote is as follows:

1. Upgrade all the minibuffer prompts of Denote: For the time being, this means that we show a preview of the file to-be-linked or to-be-opened. Simply enable the consult-denote-mode. The prompts use the same patterns of interaction as core Denote and will never deviate from this paradigm, such as to prettify titles or whatnot (that is an expensive operation that slows down Emacs).

2. Easy search for the denote-directory: Implement Consult-powered Grep and Find commands which operate on the denote-directory regardless of where they are called from. See the commands consult-denote-grep and consult-denote-find. Customise which command they call by modifying the user options consult-denote-grep-command and consult-denote-find-command.

3. Include Denote "sources" for consult-buffer: This is also part of the consult-denote-mode. It adds new headings/groups to the interface of the consult-buffer command. Those lists (i) the buffers that visit Denote files, (ii) the subdirectories of the denote-directory, and (iii) the silos listed in the value of the user option denote-silo-extras-directories (for those who opt in to that extension).

In the future we may use other features of Consult, based on user feedback.