This is a very simple port of fcopy.el
Fcopystart brings you into Funny Copy mode. The place where you get in fcopy-mode is the paste point; the text you choose to copy will be inserted with Fcopyend.
Mainly written by chatgpt4. Here is the log. (Japanese) https://gist.github.com/tsukimizake/23d6fa62161642c0d430e45adc2202b2#file-gistfile1-txt
I used https://github.com/ellisonleao/nvim-plugin-template to turn this code into a plugin.