Compatibility with linkit widget

The Linkit issue was committed, so this is open for review again.

Cursory changes to make the modules load on D9 and D10.

This fixes a minor issue in the Seque submodule.

Typoo.

The last submitted patch, 11: link_class-n2905236-11.patch, failed testing. View results →
- codesniffer_fixes.patch Interdiff of automated coding standards fixes only.

The last submitted patch, 10: link_class-n2905236-10.patch, failed testing. View results →
- codesniffer_fixes.patch Interdiff of automated coding standards fixes only.

Let's list linkit as a test dependency via a require-dev line in composer.json.