[website] add rpc library links to dev resources

Summary: As requested, adding the JS and Python RPC library links to the ecash dev resources section of the ecash page.

Test Plan:
bundle exec jekyll serve
test both links

Reviewers: Mengerian, #bitcoin_abc

Reviewed By: Mengerian, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D12084