Add scheduling functionality

[herzog31]

Please always provide the GitHub issue(s) your PR is for, as well as test URLs where your change can be observed (before and after):

• Added a sidekick extension that adds a date field to preview scheduled content.
  • If you want to test this, please checkout this PR locally and update the sidekick options (advanced) to use a local config file.
• Scheduled date for sections can be added via Section Metadata block.
• Scheduling for blocks can be added via a date row.
• Empty sections will not be automatically deleted. Instead add scheduling to them.
• If a simple date is defined, the block/section will be displayed after that date.
• If a date range is defined, the block/section will be displayed only in that range.
• Not suitable for confidential data, since the scheduled content will still be in the DOM.

Example:

You can test scheduling on https://scheduling--wknd--hlxsites.hlx.live/drafts/mabecker/scheduling

Test URLs:

• Before: https://main--wknd--hlxsites.hlx.page/
• After:
  • https://scheduling--wknd--hlxsites.hlx.live
  • https://scheduling--wknd--hlxsites.hlx.live/drafts/mabecker/scheduling

[aem-code-sync]

Hello, I'm Franklin Bot and I will run some test suites that validate the page speed.
In case there are problems, just click the checkbox below to rerun the respective action.

• Re-run PSI Checks

[aem-code-sync]

Page	Scores	Audits	Google
/
/drafts/mabecker/scheduling

[pnamadobe]

hi, i have customers asking about this. is there a rough timeframe for this to get into main?
Also, what if we hash the (not yet published) text with a key that is fetched. async and the key is only published at the appropriate time?
nvm. that would probably kill performance scores.

[herzog31]

@pnamadobe this implementation will stay in block party mode. Feel free to copy the code over to your project.