sc-70154-update-qml-readme-to-highlight-image-standards

[ashishks0522]

Ticket

• sc-70154-update-qml-readme-to-highlight-image-standards

Changes

• Add instructions to README.md about image standards to be followed while writing demos this QML repository.
• Requirements sources from this doc
• Since QML is public & the notion doc is private (accessible by Xanadu only) added the relevant standards in text form in the README.md

Preview

• https://github.com/PennyLaneAI/qml/blob/2e9da1bb2bef3cd8a2eb504459f686ab20b9ec0c/README.md