Add explanation about healthcheck_repo

Signed-off-by: Alice Ferrazzi <alice.ferrazzi@miraclelinux.com>

README.md

@@ -223,6 +223,7 @@ masters:
  pg_lava_password: The Postgres lavaserver password to set
  http_fqdn: The FQDN used to access the LAVA web interface. This is necessary if you use https otherwise you will issue CSRF errors.
  healthcheck_url: Hack healthchecks hosting URL. See hosting healthchecks below
+ healthcheck_repo: Hack healthchecks git repository URL. See hosting healthchecks below
  build_args:
  - line1 A list of line to set docker build-time variables
  - line2
@@ -514,6 +515,13 @@ One master and slave on DC A, and one slave on DC B.
 Both slave need to have healthcheck_host to true and master will have healthcheck_url set to http://healthcheck:8080
 You have to add a DNS server on both slave with an healthcheck entry.
 
+For mirroring the healthcheck repository and keeping it local
+
+- Mirror https://github.com/BayLibre/lava-healthchecks-binary to your repository of choice
+- Add your local boards healthchecks binary
+- Set the repository to your new repository using healthcheck_repo on the master
+- Rebuild healthchecks docker container
+
 ## Bugs, Contact
 The prefered way to submit bugs are via the github issue tracker
 You can also contact us on #lava-docker on the Libera.chat IRC network