Display thumbnails for .TIFF resources

[alukach]

Proposed changes in this pull request

Strangely, we opt to display a generic thumbnail for resources where instance.mime_type == image/tiff.

There may be a story behind this, I'm unsure. However, looking at my dev machine, it appears that thumbnails for TIFF images do get generated correctly. I believe we should display those thumbnails rather than the generic thumbnail.

When should this PR be merged

Anytime

Risks

There's likely a good reason why we don't currently display .TIFF thumbnails. This was added in #688 as a solution to #668. I'm not sure why this was, perhaps @clash99 can comment on this.

Follow-up actions

None

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[oliverroick]

Some browsers (like Chrome) don't display TIFF images. When we create thumbnails we don't convert the type to something more compatible (PNG for example), so the tumbnail won't show:

[alukach]

Thanks @oliverroick, that makes sense. Closing.

[clash99]

Sorry I didn't comment earlier @alukach - just saw this.