All Submissions:

• Have you followed the WooCommerce Contributing guideline?
• Does your code follow the WordPress' coding standards?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Changes proposed in this Pull Request:

• Adds the option to filter notes in the REST endpoint using is_read
• Adds the option to filter notes by is_read in the data store
• Uses the unread notes count in the inbox panel header
• Adds logic to mark notes as read when viewing a note

@pmcpinto @jarekmorawski This PR marks notes as read when viewing them. One issue with this is that a note is instantly marked as read and the unread indicator flashes off the screen almost immediately. It might be worth adding a delay before this occurs or caching the notes read status temporarily to avoid losing the unread indicator immediately.

Also cc @moon0326 to make sure I'm not creating regressions with the existing logic. It seems like a choice was made in woocommerce/woocommerce-admin#6047 and woocommerce/woocommerce-admin#7896 to only mark notes as read when they were actioned. This obviously undoes some of that work, but we are unlikely to see read notes if they are not actioned.

Closes #34929 .

• This PR is a very minor change/addition and does not require testing instructions (if checked you can ignore/remove the next section).

How to test the changes in this Pull Request:

1. Create a site with at least 1 or more unread notes
2. Visit the home page and scroll down to see the notes
3. Note that unread notes are marked as read on viewing
4. Note that the count of notes in the inbox panel header reflects unread notes (all unread notes, not just the visible ones prior to loading the remaining notes).

Other information:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes, as applicable?
• Have you created a changelog file for each project being changed, ie pnpm --filter=<project> changelog add?

FOR PR REVIEWER ONLY:

• I have reviewed that everything is sanitized/escaped appropriately for any SQL or XSS injection possibilities. I made sure Linting is not ignored or disabled.