Suggestion: Add the ability to pass a loading indicator to the file viewer

[HappyTreesDev]

As it sits, the loading indicator is not editable. It would be nice to be able to brand the loading indicator to match the rest of my application. This could be solved by adding the ability to pass a loading indicator component to the FileViewer component as a prop.

An example would be:

<FileViewer fileType="gif" filePath="pathToFile" loadingIndicator={MyLoadingIndicator} />

[HappyTreesDev]

I was going to take a crack at adding this feature in a pull request but I can't seem to test my code changes due to being on windows and it seems make is needed to run anything.

[d4mr]

This would be a really great feature. +1