Add ultyas to the README.md file

[jamescherti]

Add ultyas to the README.md file

Ultyas is a command-line tool that simplifies the process of converting code snippets from UltiSnips (Vim/Neovim) to YASnippet format (Emacs).

Ultyas can be used for the following purposes:

• Migrating your snippets from UltiSnips to YASnippet format.
• Maintaining consistent snippets across both Vim/Neovim and Emacs. (For instance, the author of Ultyas effortlessly switches between Vim and Emacs depending on the machine and environment, ensuring that the same snippets are accessible in both editors.)