Update contribution instructions to refer to Visual Studio Code

[wwoast]

I've hit the point where I realize RPF will never be done if it's just me working on adding photos and animals.

Document all the Git/update workflows clearly enough such that technical novices have enough information to download VS Code, and do any of the typical panda update workflows. Specifically cover:

• All relevant keystroke shortcuts for navigation
• All common shortcuts to use IDE features to double-check panda names
• A Git branching workflow that doesn't require any knowledge of the command-line
• The people structure of how updates work (I am still BDFL for what lands in master)

Also clearly document strategies for validating assumptions about who a panda is (google / news search / YouTube).