Add space for executable construction icon

[Mersid]

Continuation of #1056, which was closed due to incorrect branch. We should find a way to dynamically calculate the size so we don't have to go around adding spaces like this.

Makes executable files go from looking like this:

To this:

Notice in the original image there's no spacing between the construction crane icon and the file's name.

---

TODO

• Use cargo fmt
• Add necessary tests
• Update default config/theme in README (if applicable)
• Update man page at lsd/doc/lsd.md (if applicable)

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