Add emoji support

[calve]

Add a new emoji theme, using emojis as file icons. Icons are set depending of the file extension

Rendering depends of the font used and may differ between users. Most emojis width are twice as a single ASCII character, it's up to the terminal application to render them accordingly.

Example display :

📁..                |
📂icons/            |
  📄close.xpm       |
  📄leaf.xpm        |
  📄open.xpm        |
📂screenshots/      |
  🌄icons.png       |
📂test/             |
  🐏neotree-test.el |
  🐏test-buffer.el  |
  🐏test-cmds.el    |
  🐏test-utils.el   |
  🐏test-vc.el      |
📄LICENSE           |
🔧Makefile          |
📘README.md         |
🐏neotree.el        |

[calve]

Hi ! This is my very first emacs-lisp contribution, so maybe some code can be simplified ?

[milouse]

@Abdisalan can I ask why this MR has been closed? Do you reject the feature or is it just because the MR is very old and this branch would need a rebase? If the later, please let me know, I’d provide such a rebase on last dev version.

[Abdisalan]

@milouse I closed it because this feature is already covered by the all-the-icons package integration. If you want icons in the terminal, I think a better solution would be to have something like all-the-icons so that the icons match the file extension better and is more comprehensive.

This PR only supports ~30 extensions and a lot of the emojis either don't really match the extension or have a duplicate wrench which makes it confusing.