[DOC] add link to troubleshooting in Install selector tool

[raybellwaves]

Report needed documentation

Describe the documentation you'd like

The selector tool (https://docs.rapids.ai/install#selector) for installing RAPIDS is great. In #488 (comment) there was a little discussion about where would be best to put some of the troubleshooting advice for CUDA version for a conda install e.g. https://docs.rapids.ai/install#system-req or https://docs.rapids.ai/install#troubleshooting. I'm still not sure on where is the best location but one thing I think may help would be a link in the selector to the troubleshooting section after the copy button. However, there may be a need for duplicated documentation if it takes to you separate sections e.g. conda and docker which isn't ideal.

[bdice]

This is a great idea. I will see if I can add this.