Consider adding a notice to discourage IE11 usage

[youknowriad]

For PHP upgrades, nudging users to update their PHP version proved to be successful.

Maintainability cost of IE11 (In terms of time, bundle size and a lot more) is very high and IE11 is approaching the 1% threshold in its usage worldwide ​https://caniuse.com/usage-table

I think we should consider adding a notice to discourage its usage.

[johnbillion]

This sounds like it should be a meta ticket to add a message to Browse Happy that shows up to IE11 users. See wp_dashboard_browser_nag().

[youknowriad]

@johnbillion I created this ​https://meta.trac.wordpress.org/ticket/4863 should we close this one?

[afercia]

Now that the browsehappy API has been updated (see ​https://meta.trac.wordpress.org/ticket/4863) the dashboard notice "nag" will be displayed to Internet Explorer 11 users. See attached screenshot.

The notice message needs to be updated as it still refers to:

• "you're using an insecure version of Internet Explorer"
• "Update Internet Explorer"

[davidbaumwald]

This ticket still needs a decision and possible patch, and with 5.4 Beta 1 landing today, this is being moved to Future Release. If any maintainer or committer feels this can be included in 5.4 or wishes to assume ownership during a specific cycle, feel free to update the milestone accordingly.

[netweb]

Related: #49696 Define guidelines for minimum IE support