[subresource-integrity] 各種更新

Prepare for an FPWD of SRI2.
w3c/webappsec-subresource-integrity@66e3d41

Describe the integration with link headers.
w3c/webappsec-subresource-integrity@ac31b01

Specify the supported hashing algorithms.
w3c/webappsec-subresource-integrity@abca59a

Editorial updates
w3c/webappsec-subresource-integrity@0f7980a

Author: triple-underscore