CI: markdown link checker (#7145)

* change (CI): markdown link checker

* Fix some invalid doc links (re-run of cargo-unleash gen-readme w/ fixes).

* Fix some invalid doc links

* Fix some invalid doc links

* Fix some links

* Fix some links

* Apply @bkchr suggestions from code review

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* Fix more links

* Fix more links

* typo

* Fix more links

* Fix more links

* Ignore valid link .. check wrongly sees it as invalid

* Fix style issue

* Fix style issue

* change (CI): update style guide link

* change (lib): suggestions

Co-authored-by: Dan Forbes <dan@danforbes.dev>
Co-authored-by: Steve Degosserie <steve@parity.io>
Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

substrate/bin/node-template/README.md

@@ -55,7 +55,7 @@ RUST_LOG=debug RUST_BACKTRACE=1 ./target/release/node-template -lruntime=debug -
 ### Multi-Node Local Testnet
 
 To see the multi-node consensus algorithm in action, run a local testnet with two validator nodes,
-Alice and Bob, that have been [configured](/bin/node-template/node/src/chain_spec.rs) as the initial
+Alice and Bob, that have been [configured](./node/src/chain_spec.rs) as the initial
 authorities of the `local` testnet chain and endowed with testnet units.
 
 Note: this will require two terminal sessions (one for each node).