docs: additional information on gradle-lite (#10640)

Signed-off-by: Alexandra Guironnet <alexandra.guironnet@rte-france.com>
Co-authored-by: HonkingGoose <34918129+HonkingGoose@users.noreply.github.com>
Co-authored-by: Michael Kriese <michael.kriese@visualon.de>

lib/manager/gradle-lite/readme.md

 `gradle-lite` is an an alternate manager for Gradle, and is written in JavaScript.
-The main benefit of `gradle-lite` is that it doesn't need to invoke the `gradle` tool from and command line in order to extract dependencies.
+The main benefit of `gradle-lite` is that it doesn't need to invoke the `gradle` tool from the command line in order to extract the dependencies.
 
 To enable `gradle-lite`:
 
@@ -18,3 +18,25 @@ To disable the original `gradle` manager if `gradle-lite` satisfies all requirem
 ```
 
 Feedback for this manager would be welcome as we would like to switch it to be the default manager for Gradle soon.
+
+`gradle-lite` supports the following version definition strategies:
+
+- Version defined as a plain string in a `*.gradle` file, for example: `"org.springframework.boot:spring-boot-starter-web:2.5.1"`
+
+- Version defined as a local variable:
+
+  - In `build.gradle`:
+
+    ```
+    def springBoot='2.5.1'
+    ...
+    "org.springframework.boot:spring-boot-starter-web:$springBoot"
+    ```
+
+- Version defined as a variable in the accompanying `*.properties` file:
+  - In `gradle.properties`: `springBoot=2.5.1`
+  - In `build.gradle`: `"org.springframework.boot:spring-boot-starter-web:$springBoot"`
+
+Variables defined in other custom locations are not supported.
+
+See the [Gradle documentation](https://docs.gradle.org/current/userguide/build_environment.html#sec:gradle_configuration_properties) for details on defining variables.