shebang to run script with ./script notation

[tallguyjenks]

this doesnt affect present functionality of script, but allows someone (like me) to

chmod +x obsidian_to_anki.py
./obsidian_to_anki.py

[Pseudonium]

Hmm, this does seem useful, but it's not something I'd want to roll out to all users. Also, presumably this would depend on where python is stored, and which version of python you want to specify? I'm not too familiar with shebang notation.

I'll add it as a suggestion to README.md though.