Fix label spacing theme issue in header and link foreground color issue in dark mode

[taldekar]

Description of changes:

• The feedback dialog header has a spacing problem where the link labels and the text labels don't have spaces between them on windows. Fixed this issue by adding a custom space between labels for different platforms.
• The optional text was updated to be light gray.
• The optional label is too close to the border. A grid margin was added inside the comment box that improves spacing inside the comment box.
• The links do not have the right foreground color in dark mode. Fixed this issue by using the Link widget instead of Label.

Screenshots

• Windows:

• MacOS:

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