[Bengali] Corrections to the history section

As suggested by Sankarshan in mailing list
https://groups.google.com/d/topic/indicfontbook/GJ1qlu4_quQ/discussion
Better title for the document

As suggested by Sankarshan in mailing list
https://groups.google.com/d/topic/indicfontbook/GJ1qlu4_quQ/discussion
Fix a build error introduced by wordwrapping the image URL