Fix incorrect y-coordinate when drawing text-box

[Saba-Sabato]

Hi! Really appreciate this package, thanks.
Following the fix in #6 , we need to update the y-coordinate for drawing the textbox too.
I have also added some tests and docs, if this is too much feel free to drop the other commit or edit as you see fit. Thanks!

[straussmaximilian]

Hi,
this is great, thanks!
I made a couple of adjustments:

• Typing caused issues with Python 3.8, so I made it backward compatible
• I changed the test a bit to know which word fails
• For some reason, there were slight differences in the test images, so tests failed
• I made the tests more specific by adding the language preference
• I made a confidence parameter to filter out based on confidence
• This still didn't fix the issue, so I now included an MSE score to roughly compare the images.

For some reason it didn't push to this branch, so the PR is now here #10

[Saba-Sabato]

Thanks for taking the time to go over it and make the required corrections!