Menu-label values should allow spaces before a list item

[jthegedus]

Describe the bug

CSV values for select-menu-labels cannot have spaces following commas. Whitespace trimming after splitting on , should allow this.

Steps to reproduce

<!-- select-menu-labels: Operating System, Installation Method -->

produces two menus, with id's as:

<select id="operating-system">
...
<select id="-installation-method">

Expected behavior

Installation Method should not be prefixed by a hyphen -

Screenshots

Additional context