fix: (Platform) adding button pressed markup to panel documentation

[krosenk729]

Please provide a link to the associated issue.

fixes: #3493

Please provide a brief summary of this pull request.

adding button pressed markup to panel documentation

Please check whether the PR fulfills the following requirements

• the commit message follows the guideline:
  https://github.com/SAP/fundamental-ngx/blob/master/CONTRIBUTING.md
• tests for the changes that have been done
• all items on the PR Review Checklist are addressed :
  https://github.com/SAP/fundamental-ngx/wiki/PR-Review-Checklist

Documentation checklist:

• update README.md
• Breaking Changes Wiki
• Documentation Examples
• Stackblitz works for all examples

[CLAassistant]

All committers have signed the CLA.

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[droshev]

@krosenk729 Thank you for your PR! Would you mind singing the CLA so we can merge the PR?

[krosenk729]

@droshev done! sorry for the delay - had to use a different browser for it :)

could you add a hacktoberfest-accepted label to this PR? no worries if you all aren't participating and the answer is 'no'

thanks again

[droshev]

@droshev done! sorry for the delay - had to use a different browser for it :)

could you add a hacktoberfest-accepted label to this PR? no worries if you all aren't participating and the answer is 'no'

thanks again

@krosenk729
I added the label, the CLA seems not kicking

[droshev]

@krosenk729 - can you re-try CLA? i know sometimes it doesn't kick in

[krosenk729]

@droshev done! it's still pending. is there anything else I should try? thanks

[KharitonOff]

The commits in this PR are made by @katherinefhc. @krosenk729 please, make sure that @katherinefhc signs the CLA too.

[katherinefhc]

fixed! thanks for your patience