Add an option to open a file from the FileSystem dock with a single click

[Kalabasa]

Describe the project you are working on:
Demo pong project to check out Godot.

Describe the problem or limitation you are having in your project:
Opening a file from the Filesystem tab requires an extra click in quick succession. I'm used to opening files in a single click because it's less strain on the wrist.

Describe the feature / enhancement and how it helps to overcome the problem or limitation:
Open a file with a single click. This will remove the extra time-based click required to open a file.

Describe how your proposal will work, with code, pseudocode, mockups, and/or diagrams:
Quick solution would be to add an option to "automatically open files when selected" in the Filesystem tab.

Better solution would be to set a consistent preference for opening things in lists in the Editor (Related #1507).

Here's a similar setting in VSCode

If this enhancement will not be used often, can it be worked around with a few lines of script?:
Pressing Enter after highlighting the file is a workaround.

Is there a reason why this should be core and not an add-on in the asset library?:
It's the Editor UI.

Also, double-clicking is difficult for some people, especially those who lack specific fine motor ability. It could at least be an accessibility option.

[Calinou]

If we support this, this should probably be a global toggle for most actions that currently require a double-click. Selecting items would be done by hovering them for a certain period of time instead.

For examples of implementations out there, see Windows Explorer (disabled by default) or KDE Plasma (enabled by default).

On second reading, it seems this proposal is about opening files on a single click, not directories. Keep in mind this may still interfere with selection…