The compatibility matrix for SCM v13 is here: https://support.ca.com/us/product-content/status/compatibility-matrix/ca-harvest-software-change-manager-v13_0-compatibility-matrix.html
The supported browser versions for Harweb, as listed on the Compatibility Matrix are: Microsoft Internet Explorer versions 9, 10 and 11, and Firefox all versions up to 33. I believe all these browser versions support HTML5.
There is nothing in the documentation about whether, or not specific compatibility testing has been done to confirm HTML5 support. If you would like to have this specific compatibility testing, it will be best to post your request as an "Idea".
Let me know if this is the information you needed.