Code folding

Sometimes we'd like to ignore the details of code blocks when reading to absorb a high-level overview of a file quickly.

It is very helpful if the long code blocks can be folded by clicking the arrow next to the line number.

For example, note the difference starting from line 12.

Folded	Unfolded

You can toggle this feature via ⚙️settings -> More -> Fold source code button.

I've been using another extension for the similar feature, but it is out of maintenance. So now I decide to implement it in Gitako.