At its face this looks like a good idea, but given the hassle of injecting the new checksum in the base file for every change I doubt it will be done by anyone but the most security conscious companies.
1. Not many people hand-write HTML tags these days, they tend to get generated at the level of apps like WordPress (which already has an SRI plugin) or frameworks like Rails (which can already do things like javascript_include_tag :application, integrity: true).
2. The people who do hand write HTML tags tend to be precisely the type of people who would go out of their way to generate an md5 checksum on the commandline, or write a script to post process their HTML files.
2. The people who do hand write HTML tags tend to be precisely the type of people who would go out of their way to generate an md5 checksum on the commandline, or write a script to post process their HTML files.