Add instructions for running mdbook linkcheck (#238)

* Update config to support linkcheck

Allows checking if all relative links inside the mdBook are valid.
Especially useful for ensuring updated links when moving content around.


* Add section explaining link check to readme

README.md

@@ -22,3 +22,12 @@ To install mdBook use the following link if:
 
 - [you have Rust toolchain installed](https://rust-lang.github.io/mdBook/guide/installation.html#build-from-source-using-rust)
 - [you **DON'T** have Rust toolchain installed](https://rust-lang.github.io/mdBook/guide/installation.html#pre-compiled-binaries)
+
+#### mdBook-linkcheck
+Additionally there's a community-made package that you can use alongside mdBook to show you some potentially broken links in markdown files called [mdBook-linkcheck](https://github.com/Michael-F-Bryan/mdbook-linkcheck)
+
+Although not required, you may find it helpful to use alongside mdBook to ensure you've linked things properly
+
+To install mdBook-linkcheck use the following link if:
+- [you have Rust toolchain installed](https://github.com/Michael-F-Bryan/mdbook-linkcheck#getting-started)
+- [you DON'T have Rust toolchain installed](https://github.com/Michael-F-Bryan/mdbook-linkcheck/releases/latest) (add `mdBook-linkcheck.exe` to the same folder `mdBook.exe` is located)

book.toml

@@ -6,3 +6,8 @@ language = "en"
 multilingual = false
 src = "docs"
 title = "Northstar Wiki"
+
+[output.html]
+
+[output.linkcheck]
+optional = true