Add Ctrl+U shortcut

[nuckle]

Description

Closes this issue - #1689

Screenshots

Before pressing Ctrl+U

After pressing Ctrl+U

Additional information

This shortcut needs to be listed here - https://github.com/JustArchiNET/ASF-ui/wiki/Features#shortcuts

Checklist

• My pull request is not a duplicate
• I added a descriptive title to this pull request
• I added a concise description or a self-explanatory screenshot to this pull request
• My code follows the code style of this project
• I have performed a self-review of my own code

[Aareksio]

If nextTick works here, I'd use it instead of setTimeout

[nuckle]

Like so?

      jumpToStart() {
        const el = this.$refs['terminal-input'];
        if (el.setSelectionRange) el.setSelectionRange(0, 0);
      },

      deleteBeforeCursorAndJumpToStart() {
        this.removeBeforeCursor();
        this.$nextTick(() => {
          this.jumpToStart();
        })
      },

[Aareksio]

I'd just replace setTimeout with next tick:

if (el.setSelectionRange) {
  this.$nextTick(() => el.setSelectionRange(0, 0));
}

I do not know why you require setTimeout in the first place, but nextTick should achieve similar result