Build pipeline - manifests

[FostUK]

Apps use a games manifest generated during the build. Storybook also has an updated one that created manifests per theme so they can be downloaded separately.

Moving these into the genie repo and build would have the advantage of one place for them to be updated and fixed where necessarily as currently they are part of each repo's build.sh

[SmileyJames]

Relevant Code: https://github.com/bbc/cbeebies-genie-storybook/blob/master/build-scripts/generate-manifest.js

Possibly this is going to affect Get Creative? Might be worth researching if we have similiar issues with that genie game pipeline. If it does affect it, maybe the solution is to move the responsibility to genie's main repo as @FostUK suggests