[DOC]: Update ROADMAP page to include current plan

[acostadon]

How would you describe the priority of this documentation request

Critical (currently preventing usage)

Please provide a link or source to the relevant docs

https://docs.rapids.ai/api/cugraph/nightly/basics/cugraph_intro/#roadmap

Describe the problems in the documentation

ROADMAP section contains no valuable information and the github link is broken.

Find the best current ROADMAP information and create a customer facing document to explain what cuGraph is working on.

(Optional) Propose a correction

No response

Code of Conduct

• I agree to follow cuGraph's Code of Conduct
• I have searched the open documentation issues and have found no duplicates for this bug report