Update examples

[duncandewhurst]

Related issues

• [Schema] review for camelCase field names that should be snake_case #198

Description

This PR:

• Updates the examples to reflect the field name changes in 198 field names camelcase to snakecase #233
• Updates the PR template with a prompt to update examples when adding, removing or renaming fields
• Updates .gitmodules to use the main branch of Flatten Tool now that Remove restriction on CSV filename length OpenDataServices/flatten-tool#428 is merged

Merge checklist

• Update the changelog (style guide)
• Run ./manage.py pre-commit

If you added, removed or renamed a field:

• Update the collapse option of the jsonschema directives for dataset, resource, hazard, exposure, vulnerability and loss on reference/schema.md
• Update the diagrams in reference/schema/md

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See how to resolve check failures.

[odscjen]

Realised there was an instance of disaster_identifier that needed corrected so have added that to this PR