Cake Wallet Linux beta build instructions

Cake Wallet Linux is in beta, and the build instructions are currently a little hard to find. Until the branch for Linux is merged into main, you can find the build instructions here:

https://github.com/cake-tech/cake_wallet/pull/894/files#diff-509f42a02ccd59124dfa4b691dcd86233f137907317c0f66e6e6e7916c4c3d10

Happy building!