Revamp the Readme of the minimal template (#4649)

- Addresses
[this](https://github.com/paritytech/polkadot-sdk/issues/3155#issuecomment-2126934939).
- Technical content got adopted from the existing [solochain
readme](https://github.com/paritytech/polkadot-sdk/tree/master/templates/solochain).
  - Updated some broken links there.
- The docker instructions will work after
https://github.com/paritytech/polkadot-sdk/pull/4637.
- See the [rendered
version](https://github.com/paritytech/polkadot-sdk/blob/rzadp/minimal-template-readme/templates/minimal/README.md

).

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Co-authored-by: gupnik <[email protected]>