Add relevant RPC examples to docs

[enaples]

Important

26.09 FREEZE August 5th: Non-bugfix PRs not ready by this date will wait for 26.12.

RC1 is scheduled on August 17th

The final release is scheduled for September 7th.

Checklist

Before submitting the PR, ensure the following tasks are completed. If an item is not applicable to your PR, please mark it as checked:

• The changelog has been updated in the relevant commit(s) according to the guidelines.
• Tests have been added or modified to reflect the changes.
• Documentation has been reviewed and updated as needed.
• Related issues have been listed and linked, including any that this PR closes.
• Important All PRs must consider how to reverse any persistent changes for tools/lightning-downgrade

Ref. Issue #9294

TODO:

• currencyconvert
• splicein
• createproof
• clnrest-register-path
• sendamount
• graceful
• askrene-remove-channel-update
• currencyrate
• spliceout
• askrene-bias-node
• bkpr-report
• xkeysend
• listcurrencyrates
• delnetworkevent
• cancelrecurringinvoice
• listnetworkevents
• injectonionmessage