Add GenericName to desktop entry

[japanoise]

Thank you for creating Lagrange - it makes browsing Gemini much more pleasant!

This is a simple change to the .desktop file on Linux. The "GenericName" field is a generic description of what the program does. Some launchers allow you to search by this, which is very useful for those of us that struggle to remember things - if I haven't gone on Gemini in a while and I forgot the name of Lagrange, I can just type "gemini" into my launcher, and Lagrange will come up.

Similar uses are in Emacs:

[Desktop Entry]
Name=Emacs
GenericName=Text Editor

Hexchat:

[Desktop Entry]
Name=HexChat
GenericName=IRC Client

Firefox:

[Desktop Entry]
Version=1.0
Name=Firefox Web Browser
GenericName=Web Browser

...and many other programs besides.