docs: Update "Images, Files & Video" & link titles in sidebar

[andersonnguyen]

Description

Updated sidebar titles and breadcrumb titles of items listed under the "Images, Files & Video" section of the docs to adhere to the Gatsby Style Guide.

Changes include:

• Revising sidebar titles to use title case
• Revising breadcrumb titles to use title case
• Adding suggestions for breadcrumb titles where breadcrumb titles weren't already provided

Related Issues

Related to #18284

[wardpeet]

Thanks! I've added a few remarks to make the breadcrumb titles a bit nicer.

[wardpeet]

Looks alright to me, thanks for doing the work @andersonnguyen!

[gatsbot]

Holy buckets, @andersonnguyen — we just merged your PR to Gatsby! 💪💜

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