Error: start work failed because of a space at the end

[Hugo Cabel]

When starting working in a issue, I wanted to rename the branch because the name was too long, and forget a ending white-space.
So when clicking on the 'start work' button it failed because the name was not valid. (and it was difficult to see that they were a space at the end)

My suggestion:
- Highlight non valid character
- Trim trailing white spaces

VsCode extension version: v2.10.12 on windows