Add a how-to to contribute / root contribute with a note about the needed vscode versions and podman buildkit issue

[stan-dot]

https://github.com/DiamondLightSource/developer-portal/tree/main/docs/how-tos

This is the combination of versions that currently works on Diamond Linux PC

• vscode 1.85.1
• Dev Containers extension 0.327.0
• docker-compose 2.23.3

[stan-dot]

commented in gitlab issue, this seems to have been solved by the current vscode update

[stan-dot]

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