Clarify maintenance status

[djc]

It looks like the last commit was 15 months ago. Might be worth being explicit about the maintenance status for this project if the intention is that not much more work on it will be done?

[nociza]

Since there seems to be no crates out there to serve this purpose, I created this more lightweight replacement https://github.com/CoLearn-Dev/rdbc2.git

[jcbritobr]

Seems this project died suddenly. 3 Years without updates.