Change the method of get file extension.

[myafer]

trafficstars

:sparkles: What kind of change does this PR introduce? (Bug fix, feature, docs update...)

Bug fix.

:arrow_heading_down: What is the current behavior?

When the http response's Content-Type is not image and the _resizeimage is not work.

:new: What is the new behavior (if this is a feature change)?

The new method is get files extension with the file's binary data.

:boom: Does this PR introduce a breaking change?

No.

:bug: Recommendations for testing

:memo: Links to relevant issues/docs

:thinking: Checklist before submitting

• [x] All projects build
• [x] Follows style guide lines (code style guide)
• [x] Relevant documentation was updated
• [x] Rebased onto current develop

[cedvdb]

@renefloor could this be reviewed ? using magic bytes is preferred over a potentially missing extension