No absolute links to the website itself, on the website

They are easily broken and overlooked by the CI tests.

$ rg readthedocs
docs/polkadot/block-production/Babe.md
87:We assume that each validator divided their timeline in slots after receiving the genesis block. They determine the current slot number according to their timeline as exlained in [Section 4](https://w3f-research.readthedocs.io/en/latest/polkadot/block-production/Babe.html#-4.-clock-adjustment--relative-time-algorithm-). Similarly, when a new validator joins to BABE after the genesis block, this validator divides his timeline into slots as explained in [Section 4](https://w3f-research.readthedocs.io/en/latest/polkadot/block-production/Babe.html#-4.-clock-adjustment--relative-time-algorithm-).

docs/polkadot/NPoS/index.md
13:Visit our [overview page](1. Overview.md) for a first introduction to NPoS, and our [research paper](2. Paper.md) for an in-depth analysis. We also encourage the reader to visit the [token economics research section](https://w3f-research.readthedocs.io/en/latest/polkadot/Token%20Economics.html) for further information about staking rewards as well as slashings, and our [Wiki pages](https://wiki.polkadot.network/docs/en/learn-staking) for more hands-on information about the staking process.

README.md
1:[![Documentation Status](https://readthedocs.org/projects/w3f-research/badge/?version=latest)](https://research.web3.foundation/en/latest/?badge=latest)

Although the last one is probably fine, since the link says "latest version".

We should make the CI tests fail in the presence of these links.