Add unescape-safestr header to both fides-js fetch and privacy center calls

[allisonking]

Closes #3606

Description Of Changes

#3600 made the privacy-experience endpoint support a header Unescape-Safestr. This updates fides-js and privacy-center calls to include that header. (See original issue for screenshots of what this looks like without the header)

Code Changes

• Privacy center addCommonHeaders now always includes Unescape-Safestr
• Fides-js call to the privacy experience API now includes the header Unescape-Safestr

Steps to Confirm

• Edit a privacy notice to have special characters, such as ' or &. Can also edit the privacy experience copy to have those characters as well
• Spin up the privacy center and make sure your notices/experience reflect your ' and &s properly
• Visit /fides-js-demo.html to also see that fides-js renders your special characters 👍

Pre-Merge Checklist

• All CI Pipelines Succeeded
• Issue Requirements are Met
• Update CHANGELOG.md

[cypress]

Passing run #3010 ↗︎

0	4	0	0	0
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Details:

Merge 4675b2b into c169bc5...
Project: fides	Commit: 893da9056f ℹ️
Status: Passed	Duration: 00:45 💡
Started: Jun 30, 2023 3:54 PM	Ended: Jun 30, 2023 3:54 PM

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[eastandwestwind]

lgtm!