Making Offer-up Work with GHCS

[amessbee]

Changes include:

• script to make ports visible
• .devcontainer directory and file
• addition of env variables for domain and codespace name
• fix RPC and API ENDPOINTS in UI for wallet connection
• instructions addition in README

[amessbee]

@rabi-siddique can you please review this. @mujahidkay has already tested it, and I think we can merge it after you get to test it and find it reasonably stable. I added a few instructions in main README.md apart from other GHCS related changes. Thanks.

[rabi-siddique]

Getting CORS error while connecting to the wallet when using codespace:

[rabi-siddique]

My bad. I did not make the ports public. After making the ports public, I was able to connect the wallet and make the offer. There was an element of flakiness too but I am assuming it was due to my Internet. Will give it another try in a while.

Looks good overall :)