[ELPA] New package: Peek

[Meow King]

I have created a new package ~Peek~, which allows users to create a peek
view below/above cursor point to show things. 
I think it may be useful to others, so I propose it to GNU ELPA.

Package URL: https://git.sr.ht/~meow_king/peek

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More information:

Some features of it:
1. Peek view follows your cursor.
2. Buffer and window local peek views. Also capable for content sharing between 
different buffer and windows.
3. Store text of marked region, and then display it on the peek view.
4. Peek the destination of ~xref-find-definitions~.
5. ~eldoc-message-function~ and ~eldoc-display-functions~ integration.
6. Scroll up or down inside peek view.
7. live update