docs: Indexer installation

[A-Maugli]

Where in the docs is improvement needed?
Documents indexer v2, while currently indexer is v3.7.2

Describe your feedback with as much context as possible

• Obsolete doc
• Missing conceptual explanation: who does postgre db init
• What is th data flow between algod, conduit, indexer and postgre
• How can it be correctly installed under Linux, e.g. Ubuntu
• How can (if it can) be installed under Windows

[larkiny]

Thank you for raising this! We will fix this ASAP.