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/primitives/api/README.md

@@ -3,8 +3,8 @@ Substrate runtime api
 The Substrate runtime api is the crucial interface between the node and the runtime.
 Every call that goes into the runtime is done with a runtime api. The runtime apis are not fixed.
 Every Substrate user can define its own apis with
-[`decl_runtime_apis`](macro.decl_runtime_apis.html) and implement them in
-the runtime with [`impl_runtime_apis`](macro.impl_runtime_apis.html).
+[`decl_runtime_apis`](https://docs.rs/sp-api/latest/sp_api/macro.decl_runtime_apis.html) and implement them in
+the runtime with [`impl_runtime_apis`](https://docs.rs/sp-api/latest/sp_api/macro.impl_runtime_apis.html).
 
 Every Substrate runtime needs to implement the [`Core`] runtime api. This api provides the basic
 functionality that every runtime needs to export.