update docs with coding standards

[jroebu14]

Resolves NEWSWORLDSERVICE-1494

Overall change: Adds agreed set of component standards to the docs.

Replaces old coding standards doc.

TODO Still to provide some code examples for some of the standards.

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• [ ] I have assigned myself to this PR and the corresponding issues
• [ ] I have added the cross-team label to this PR if it requires visibility across World Service teams
• [ ] I have assigned this PR to the Simorgh project
• [ ] (BBC contributors only) This PR follows the repository use guidelines

Testing:

• [ ] Automated (jest and/or cypress) tests added (for new features) or updated (for existing features)
• [ ] If necessary, I have run the local E2E non-smoke tests relevant to my changes (CYPRESS_APP_ENV=local CYPRESS_SMOKE=false yarn test:e2e:interactive)
• [ ] This PR requires manual testing

[RetiredBlob]

It's surprisingly hard to come up with bad examples