Add 'add text to gemini' function

Now you can add text to gemini by selecting the text and hitting <leader>sg.
If you try to send it before have initialized the plugin, it will as you to do it first

Change README.md

To solve what was raised on #3, I've changed the README.md so it has the right plugin name

Fix issue with node @google/gemini-cli

Fixes the following issue

• #2

v1.0.0

First stable release

• toggles gemini buffer with <leader>og

Full Changelog: https://github.com/JonRoosevelt/gemini.nvim/commits/v1.0.0