Updated .gitignore to ignore thumbs.db
Updated .gitignore to ignore thumbs.db

Thumbs.db weren't being ignored in SourceTree, presumably because there was a space after the line...

akorentlab/tesseract,charlesw/tesseract,bing6/tesseract,nguyenq/tesseract,beni55/tesseract,Capibara-/tesseract,anshul1912/tesseract-1