Support files without extensions in importFromUrl

[wladif]

This fixes the enhancement #1652.
It extends the importFromUrl logic to support importing of images from URLs without any extension.

Caveats:

1. the constant SAMPLE_DOWNLOAD_TIFF_WITHOUT_EXTENSION needs to be updated to point to Lychee repo once this PR is merged. I'll do in a future PR.
2. Unfortunately, Github sets the content type to application/octet-stream when file doesn't have an extension, this means that the branch elseif (isset($originalMimeType) && self::isSupportedMimeType($originalMimeType)) is not covered by current tests. If you know a provider/way to host the sample files (mongolia & tiff) without extension so that the web server will set the Content Type correctly (e.g. image/jpeg), please let me know and I'll add the tests. Thanks!

[codecov]

Codecov Report

Merging #1873 (5467065) into master (1a0b831) will decrease coverage by 0.48%.
The diff coverage is 83.78%.

Additional details and impacted files

[ildyria]

To make it easier for you in the future, I suggest when you want to add a feature to create a new branch instead of doing it on master on your side :)
A bit of doc is here: https://lycheeorg.github.io/docs/contributions.html#how-to-properly-submit-a-pull-request-to-lychee

[wladif]

Cool! Thanks! Is there any issue that I still need to address?