gha: Add update static files workflow

[philipnbbc]

Details

Brief description of what this PR does.

Pivotal Story

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Related PRs

Where appropriate. Indicate order to be merged.

Links to external test runs/working deployment

Where appropriate, if separate to default CI run

Submitter PR Checks

(tick as appropriate)

• PR completes task/fixes bug
• Tests exercise code appropriately
• New features and API breaks are flagged in commit messages using magic strings
• Documentation updated (README, Confluence, Docstrings, API spec, Engineering Guide, etc.)
• Downstream repos have been checked for potential breaks & fixed as needed
• APIs/UIs/CLIs updated as required
• PR added to Pivotal story
• Follow-up stories added to Pivotal
• Any temporary code/configuration removed (e.g. test deployment environment, temporary commontooling branch)
• Any pins against pre-releases have been removed

Reviewer PR Checks

(tick as appropriate)

• PR completes task/fixes bug
• Tests exercise code appropriately
• Design makes sense, and fits with our current code base
• Code is easy to follow
• PR size is sensible
• Commit history is sensible and tidy

Info on Cloudfit PRs

• The checks above are guidelines. They don't all have to be ticked, but they should all have been considered.
• For more details on how to asses PRs, see: https://github.com/bbc/rd-apmm-docs-ways-of-working/blob/master/workflow/PRChecklist.md

[AndrewGibb]

LGTM