Minor edit to a broken link for Rust Docs on the README.md

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

Was constantly failing, so here a fix.

This one also works and it is easier.

..and other high level docs.


# Polling 

Please vote in the reactions of this PR 

- 👍 I agree to replace the website of this repo to
https://paritytech.github.io/polkadot-sdk/master/polkadot_sdk_docs/index.html
- 👎 Keep it as polkadot.network
- 🤷

 Different opinion

---------

Co-authored-by: Bastian Köcher <git@kchr.de>

Co-authored-by: Liam Aharon <liam.aharon@hotmail.com>
Co-authored-by: Bastian Köcher <git@kchr.de>

Writing down the processes to do our releases.

Status: please review & approve so we can go ahead.

---------

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Co-authored-by: joe petrowski <25483142+joepetrowski@users.noreply.github.com>
Co-authored-by: Liam Aharon <liam.aharon@hotmail.com>
Co-authored-by: Bastian Köcher <git@kchr.de>
Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>
Co-authored-by: Jegor Sidorenko <5252494+jsidorenko@users.noreply.github.com>

Co-authored-by: Liam Aharon <liam.aharon@hotmail.com>

This PR is a continuation of
https://github.com/paritytech/polkadot-sdk/pull/2102 and part of an
initiative started here https://hackmd.io/@romanp/rJ318ZCEp
What has been done:
- The content under `docs/*` (with the exception of `docs/mermaid`) has
been moved to `docs/contributor/`
- Developer Hub has been renamed to Polkadot SDK Docs, and the crate has
been renamed from `developer-hub` to `polkadot-sdk-docs`
- The content under `developer-hub/*` has been moved to `docs/sdk`

---
Original PR https://github.com/paritytech/polkadot-sdk/pull/2565, it has
been close due to too many rebase conflicts

---------

Co-authored-by: Serban Iorga <serban@parity.io>
Co-authored-by: Chevdor <chevdor@users.noreply.github.com>
Co-authored-by: Egor_P <egor@parity.io>
Co-authored-by: Bastian Köcher <git@kchr.de>

* Add markdown linting

- add linter default rules
- adapt rules to current code
- fix the code for linting to pass
- add CI check

fix #1243

* Fix markdown for Substrate
* Fix tooling install
* Fix workflow
* Add documentation
* Remove trailing spaces
* Update .github/.markdownlint.yaml

Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
* Fix mangled markdown/lists
* Fix captalization issues on known words

* Added root README.md draft

* Modified Contribution section to reflect unified guidelines

* Update README.md

Co-authored-by: Squirrel <gilescope@gmail.com>

* Expand Substrate description

* Added Badges and Upstream deps

* Fixed badge links

* Fixed CONTRIBUTING.md links, added security and resources section to root README.md

* Moved runtimes link to Polkadot section

---------

Co-authored-by: Squirrel <gilescope@gmail.com>
Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>