docs: improvements to SOL RPC docs

[letmejustputthishere]

This PR implements improvements and fixes for the documentation of the SOL RPC canister example.

[lpahlavi]

Thanks a lot for the improvements @letmejustputthishere! Super thankful to have your feedback, I think it definitely helps a lot to have the perspective of someone outside of the SOL RPC dev team for this.

[lpahlavi]

Thanks a lot for the improvements @letmejustputthishere! I believe I should have answered/addressed all of your comments. Could you please:

• incorporate the latest changes in main, and
• add a commit message (top-level comment) referencing XC-405?

🙏

[letmejustputthishere]

@lpahlavi this should be ready to review 🚀

[lpahlavi]

Thanks a lot for the improvements @letmejustputthishere! Just a couple tiny nits from my side.

[letmejustputthishere]

@lpahlavi thanks for the feedback! i implemented the changes, let me know if you find something else :)

[lpahlavi]

Thanks a lot for the improvements @letmejustputthishere! Just one tiny comment from my side, otherwise LGTM!