Adds an option to keep the active line highlighted even when text
inside the line is selected.

So that their vertical offsets actually match the position of the
corresponding lines.

Issue #4364

And use it in the merge addon to get the proper offsets for merge buttons

Issue #4364

Issue #4353

Issue #4353

Closes #4353

Closes #4308

Issue #4288

Closes #4287

And don't block-comment inside a block comment

Closes #4208

Closes #4018

Issue #4175

Issue #4162

Closes #4148

When persistent search dialog is open, looking up commands for findNext/
Prev keys would only search the current keyMap. This commit changes this
to also look up commands in extraKeys

Searching with findPersistentNext or findPersistentPrev will
immediately run a search with the previous query, however it will throw
and error if no previous query exists. This commit fixes by preventing
the immediate execution if no previous query is set

Closes #4128

Issue #4112

To match the actual match-highlights in the editor.

Closes #4080

See https://discuss.codemirror.net/t/range-error-with-scrollpastend-addon/773

Issue #4069

Issue #4050

Closes #4056

Issue #4057

Closes #4057