Allow non-breaking space in checkbox creation

[olagjo]

Context

• When typing out point lists, you can add checkboxes by typing - [ ] as the beginning of the line
• However, this only works with "pure" spaces, not e.g. Non-breaking spaces, which MacOS inserts if you press option+space
• In many keyboard configurations, the brackets [] are on option+number-keys
• This means that it is very easy to accidentally insert a non-breaking space while typing out a checkbox, leaving you with a bullet point starting with the text [ ] (see illustration)

• This is impossible for the naked eye to spot without checking the preview after every time you write a checkbox

Suggested fix

• [ ] Allow non-breaking-spaces in the definition of checkboxes