Feature Request: Allow users to opt our of stage description alerts once seen

[samdec11]

As a user, I want to be able to acknowledge that I've read the description of a stage So that I don't have to see the alert and click on it every time I conduct a retro and move to the next stage.

By Way Of Explanation: Every time a retro transitions to the next stage, an alert pops up with a description of the stage. Once I've seen it, I don't need to see it again unless there's new information. I'd like to be able to opt out of seeing it in future retros I take part in.

Pre-requisite: https://github.com/stride-nyc/remote_retro/issues/489

Acceptance Criteria:

• [ ] The first time a user encounters a stage, the alert pops up with a description (the same as it does currently)
• [ ] The alert has a checkbox with text à la "Do not show this message again"
• [ ] If the user has checked that checkbox, they will not see that message when transitioning to its corresponding stage the next time that user is in a retro.
• [ ] If the information changes due to adding additional features to a stage, then the user sees the updated alert message (maybe indicating that information was updated?)

[vanderhoop]

adding https://github.com/stride-nyc/remote_retro/issues/489 as a pre-req to building this out, so that users have access to the stage info if needed