Things I have tried
Tried to configure the other program to produce .md files 
What I’m trying to do
I am using Obsidian with other tools and feel the freedom of using text files 
But other tools (namely clipboard manager) can sync only to .txt files. However, in Obsidian, .txt files are opened extrenally (and not indexed).
Can I configure Obsidian to handle arbitrary file extension to handle internally (as if it would be a .md file)?