## Issue Addressed
https://github.com/sigp/lighthouse/issues/2889
## Additional Info
I have checked that linkcheck has succeeded on the book built locally. 👌
```shell
$ cd book
$ mdbook serve --open
...
2022-01-14 01:13:40 [INFO] (mdbook::book): Book building has started
2022-01-14 01:13:40 [INFO] (mdbook::book): Running the html backend
$ linkcheck http://localhost:3000
Perfect. Checked 4495 links, 80 destination URLs (76 ignored).
```
Also I'll tackle running linkcheck on CI in another pull request.