Support HIF extension

[AdamMainsTL]

Description

I've come across some unsupported files from Canon cameras that have a .hif extension. These are HEIC/HEIF files with a slightly changed extension. I have no idea why Canon decided to do this. Without any changes I am able to open the images, probably because it checks the header, but I am unable to write to paths with a hif extension.

Some random articles/forum posts mentioning the HIF format in relation to Canon cameras:
https://www.cameralabs.com/jpeg-vs-heif-canon-hif-comparison/
https://www.dpreview.com/forums/thread/4558661
https://www.reddit.com/r/canon/comments/kjc6xl/new_eos_r6_owner_here_photo_files_show_up_as_hif/

Tests

I did not add tests to the project, but I did compile the library into our application on Windows and Mac environments and verified that the old version does not support writing to paths with a "hif" extension and the updated code does. Can provide more info if needed.

Checklist:

• I have read the contribution guidelines.
• If this is more extensive than a small change to existing code, I
  have previously submitted a Contributor License Agreement
  (individual, and if there is any way my
  employers might think my programming belongs to them, then also
  corporate).
• I have updated the documentation, if applicable.
• I have ensured that the change is tested somewhere in the testsuite
  (adding new test cases if necessary).
• My code follows the prevailing code style of this project.

[lgritz]

I assume that the HIF is a concession to flash memory cards with FAT filesystem that require an 8.3 filename scheme.

Looks reasonable to me. Please accept the format fix suggestion and then I'll be happy to merge.

[lgritz]

LGTM, thanks!