[improvement] Add configurable manifest caching

[eelkevdbos]

Currently, manifests are cached with 'force-cache' as fetch option. Making this configurable would allow for more dynamic applications that for example add annotations to the manifest in real time.

[stephenwf]

Should be deployed on NPM under version @canvas-panel/core@pr-611 if you would like to test. I suspect I will mint a new release soon to cover the recent dependency updates and this addition. Thank you again!