Consider caching approach changes for static assets

[jimjohnsonrollings]

Is your feature request related to a problem? Please describe.
Arising from feedback on #8916

Specifically around:

• Setting a hash in the URL so that caches can be longer but updates can be released
• Consistently setting the strict-transport-security value to a longer value

Describe the solution you'd like

• Consider the above suggestions and decide whether to implement them, or other ideas

[eagerterrier]

akamai supports query strings, so adding version ?v=1 would work if we needed quick updates. Also, happy with strict-transport-security value for now.