Previously, the Notification triggers table in Settings lacked a
direct link to documentation for 'Followed topics'.
This commit updates the AllNotifications type to include an optional
'help_link' field and adds conditional rendering in the template to
show the help icon only if 'help_link' is present.The corresponding
test has been updated to verify the presence of the help link.
This enables direct links to relevant docs, improving usability.
Fixes: #32033.
vivek-tripathi-9005
Anders Kaseorg