docs: create a concepts section and clean up overview section (dev)

[BoHristova]

What this PR does / why we need it

This PR restructures part of the OCM website (dev version). The PR includes the following changes:

• Added a Concepts section
• Moved the content from the Important Terms document to two new documents: OCM Components and OCM Coordinates
• Included a link to the OCM specification repository in the new OCM Components document
• Deleted the Important Terms document from the Overview section
• Deleted the Specifications document from the Overview section

Screenshots

Which issue(s) this PR is related to

Related to #709

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