Document JS deprecation policy

[paulholden]

What is the Moodle feature that needs documenting?

See https://moodle.atlassian.net/browse/MDLSITE-6080

• Clarify the deprecation policy rules around JS (presumably the same as for any other language)

See https://moodle.atlassian.net/browse/MDL-87867

• Expand upon the above and describe the new JS module

Is this documentation specific to a Moodle version?

None

Are you able to provide a patch for this?

No (Default)

[jrchamp]

From Moodle Dev chat:

• MDL-87867 introduces a modal popup when deprecated code is used. For better or worse, this is breaking behat tests.
• As an example, theme_boost/bs4-compat emits the deprecation seemingly even if the the bs5 attributes exist.

It would be very helpful to know what options exist for developers who are trying to maintain a single supported release branch that works with Moodle 4.5 - Moodle 6.0.