[Feature request] Search on custom sites using image's hash

[martinezjason]

Is your feature request related to a problem? Please describe.

A lot of online galleries allow the user to search the image using an md5 hash, for example:

• Danbooru and its derivatives;

• Gelbooru and its derivatives;

• e621 and its derivatives;

• There are non-booru sites too, I swear, I just can't remember any off the cuff...

Describe the solution you'd like
It would be great if you could implement an option for the user to create custom search entries by specifying URLs with templates in them, which would then be replaced by the target image's properties, such as an MD5 hash, URL, filename, etc.
For example:

• "https://example.org?url=[URL]" would be replaced to "https://example.org?url=https%3A%2F%2Fcool.site%2Fcoolimage.jpeg",

• "https://example.org?imghash=[MD5]" would be "https://example.org?imghash=944364e77f56183e2ebd75de757488e2"

• etc.

Additional context
js-md5 or js-spark-md5 libraries could be used to hash image files.