Update validator docs on tangle.docs

[drewstone]

• Broken links need fixing (https://docs.tangle.tools/docs/node/quickstart/)
• Add link checker CI action to the docs site on push/PRs
• Update pallets and remove things not added anymore (dkg-substrate pallets)
• Latest release docs update (https://docs.tangle.tools/docs/node/node-software/)
• Ensure versions are the same across pages.. ( v0.4.7, v0.4.6, v0.5.0+)
• Bonding tokens instructions unclear (https://docs.tangle.tools/docs/node/validator/requirements/)
  • Use images, link frequently to Polkadot docs, we don't need to reinvest the wheel or re-write documentation that exists somewhere else.
• Take note of Discord questions that are asked frequently (migrating session keys), add an FAQ
• Reduce writing on the docs site for running nodes/etc, use images when possible.
• Update format of FAQ (https://docs.tangle.tools/docs/faqs/), should use markdown styles more.