Document[Fix]: broken Firefox .png image

[fahrim]

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This PR implements or fixes... (explain your changes)

Icon in the description fixed the broken Firefox .png image.

This PR closes the following issues... (if applicable)

…

Does this PR require the Docs to be updated?

…

Does this PR require new tests?

No.

This branch been tested on... (click all that apply / add new items)

Browsers:

• [x] Chrome version
• [x] Firefox version
• [x] Safari version
• [x] IE / Edge version
• [x] iOS Browser version
• [x] Android Browser version