Sketchbook tree indentation

[francescospissu]

Motivation

• The indent size of the folders in the sketchbook is too small

The sketchbook structure:

Arduino/
├── Foo/
│   └── Bar/
│       └── Sketch/
│       └── Sketch_old/

was rendered:

after the changes:

• The sketches have an inappropriate indentation level

The sketchbook structure:

Arduino/
├── Foo/
│   └── Bar/
│   └── sketch_jun14a/

was rendered:

after the changes:

Change description

Updated the left padding of the icons in the sketchbook

Other information

Fix for:

• Increase Sketchbook view tree indent #1049
• In Sketchbook view, sketches are indented by the folder expansion control icon width even when there is no icon #1050

Reviewer checklist

• PR addresses a single concern.
• The PR has no duplicates (please search among the Pull Requests before creating one)
• PR title and description are properly filled.
• Docs have been added / updated (for bug fixes / features)

[per1234]

This fixes #1050 and #1049 for me. It really does make it much easier to browse a complex sketchbook.

Thanks Francesco!

[kittaakos]

Thank you!