I found a way to create Safari extension here
but this is only for 'OS X'. I wonder if there is a way to create one for the iOS.
Any help will be appreciated!
You can not make extensions for mobile safari.
On the other hand you can add bookmarklets. The article is pretty old but it should do the trick: https://code.tutsplus.com/tutorials/create-bookmarklets-the-right-way--net-18154