Add GrandNode and nopCommerce to /docs

[pavlenex]

We should add GrandNode readme.md to our documentation repository.

https://github.com/btcpayserver/grandnode https://github.com/btcpayserver/nopcommerce

[arshbot]

What is meant by "documentation repository"?

[pavlenex]

Hey @arshbot!

To avoid overlaps in our documentation repository (the one we're on now) and reduce maintenance burden, for external plugins, we fetch readme's and simply render them through our docs.btcpayserver.org

One example of how we did it is this https://github.com/btcpayserver/btcpayserver-doc/pull/1351 that looks like this https://docs.btcpayserver.org/Smartstore/ but is actually fetched from that repo.

The readme that should be rendered is - https://github.com/btcpayserver/nopcommerce/blob/main/README.md

• https://github.com/btcpayserver/grandnode /blob/main/README.md

(so two of them actually, modified the title of the issue accordingly)

Let me know if this is clear enough.

[pavlenex]

https://github.com/btcpayserver/btcpayserver-doc/pull/1374