docs: vscode support

[jeremyjs]

Notes:

• My code editor trimmed trailing whitespace from README.md automatically.
• Simply browse the second commit to see the true diff.
• This PR just adds a quick note regarding VS Code support to encourage new community members that Pact is supported by popular code editing environments and IDEs.
• Hopefully it can be merged without a second thought to avoid any friction or churn, but otherwise let me know if there's anything else to do here!

[Luzzotica]

I feel like this would be a great, easy addition to the docs.
Seeing only Atom as a supported IDE was a little disheartening when I hopped in and started trying to develop my smart contract. I bet you'll decrease adoption friction quite a bit by just merging this request.

[emilypi]

You're right!