Fixed spelling and grammar errors in README.md

[AMetIR]

• (i.e. iOS, Android and web-based technologies) -> (i.e. iOS, Android, and web-based technologies)
• in training dataset -> in the training dataset
• numpy -> NumPy
• train with generator -> train with a generator
• pretrained weights -> pre-trained weights
• equivalent to command above -> equivalent to the command above
• Will pix2code supports other target platforms/languages? -> Will pix2code support other target platforms/languages?
• counted as error. -> counted as an error.
• every platforms/languages -> every platform/language
• dedicate their time programming -> dedicate their time to programming
• AI collaborate with humans -> AI collaborates with humans