make openhabpkgversion a documented feature (#2128)

Signed-off-by: Markus Storm <markus.storm@gmx.net>

Author: mstormi

build-image/openhabian.conf

@@ -49,6 +49,12 @@ wifi_country=""
 repositoryurl=https://github.com/openhab/openhabian.git
 clonebranch=openHAB
 
+# install a specific version of openhab and openhab-addons packages
+# use the pkg version string like openhabpkgversion=5.1.2-1
+# Leaving this empty will install the latest available packages from the release repo
+# openhabpkgversion=
+
+
 # initial openHAB configuration to import (URL or filename)
 # the file needs to be a zip archive created from openhab-cli backup and placed
 # in the directory of the first SD partition

docs/openhabian.md

@@ -406,6 +406,17 @@ clonebranch="openHAB4"
 ```
 :::
 
+#### `openhabpkgversion`
+
+To install a specific version of openhab and openhab-addons packages, use the package version string.
+Leaving this empty will install the latest available packages from the release repo.
+
+::: details Example
+```
+openhabpkgversion=5.1.2-1
+```
+:::
+
 #### `initialconfig`
 
 An initial configuration file to import when setting up openHAB.