feat: add cursor layout (#878)

* Add basic implementation of "cursor" layout strategy

* Update cursor layout strategy to properly follow cursor

* feat(cursor_layout): handle previewer

* Refactor cursor layout code

* Add cursor theme

* Update readme

* Improve cursor theme and layout documentation

* [docgen] Update doc/telescope.txt
skip-checks: true

* Remove trailing whitespace

* Fix issues related with neovim and plugin api changes

* [docgen] Update doc/telescope.txt
skip-checks: true

* Allow preview width to be configured

* [docgen] Update doc/telescope.txt
skip-checks: true

Co-authored-by: Github Actions <actions@github>
Co-authored-by: cbrunel <cbrunel@sogescom.local>

README.md

@@ -545,6 +545,7 @@ We have some built in themes but are looking for more cool options.
 | Themes                   | Description                                                                                 |
 |--------------------------|---------------------------------------------------------------------------------------------|
 | `themes.get_dropdown`    | A list like centered list. [dropdown](https://i.imgur.com/SorAcXv.png)                      |
+| `themes.get_cursor`      | A cursor relative list.                                                                     |
 | `themes.get_ivy`         | Bottom panel overlay. [Ivy #771](https://github.com/nvim-telescope/telescope.nvim/pull/771) |
 
 To use a theme, simply append it to a built-in function: