Sorry not sure if this is the place to report, but
Github is broken because of CSP.
Are you guys in SE Asia? I am having trouble with githubassets.com too.
That seemed like a hiccup in GitHub's system. For me it works fine right now, and if you're expierencing issues with the GitHub platform like this you can, after checking https://www.githubstatus.com/ , contact GitHub Support.
It seems there's a difference in the encryption protocols between Github.com and github.githubassets.com.
Github assets is replying with a TLSV1 whereas Gtihub.com is TLSv1.2. This seems to be causing a security issue with some proxies (our corporate one included) and will not allow anything hosted on github.githubassets.com to be loaded.
Good research! This should be logged by moderators soon, so they can internally consider updating the protocol GitHub assets uses.