[Focus Mode] New screenshots and content for the UA string override article

[captainbrosset]

AB#47106544

[learn-build-service-prod]

Learn Build status updates of commit a764f04:

❌ Validation status: errors

Please follow instructions here which may help to resolve issue.

File	Status	Preview URL	Details
	❌Error		Details

• [Error: CannotMergeCommit] Cannot merge commit a764f041309991c84ab4d05cce6c2f451b7cc819 in branch user/pabrosse/focus-mode-override-UA of repository https://github.com/MicrosoftDocs/edge-developer into branch user/pabrosse/focus-mode-july-2023 (commit 8740d4dc8686ab62dee9a89f6debb14ef4683ded). Please follow this documentation: https://help.github.com/articles/resolving-a-merge-conflict-using-the-command-line/ to use git.exe to resolve you content conflicts locally and then push to remote.

For more details, please refer to the build report.

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