Add explanation on how to work on Gradle plugin

gradle-plugins/README.md

@@ -1,5 +1,43 @@
-JetBrains Compose gradle plugin for easy configuration
+# JetBrains Compose gradle plugin for easy configuration
 
 Environment variables:
 * `COMPOSE_GRADLE_PLUGIN_VERSION` - version of plugin
 * `COMPOSE_GRADLE_PLUGIN_COMPOSE_VERSION` - version of JetBrains Compose used by the plugin
+
+## Developing and testing
+
+In order to work on the plugin and try out the changes on a Compose project,
+a modified version of the plugin can be published to Maven local and then
+used by a project.
+
+### Publishing a snapshot to Maven local
+
+Modify `gradle.properties` and set variable `deploy.version` to something
+meaningful depending on the current compose version, such as this:
+
+    deploy.version=1.2.0-SNAPSHOT
+
+Afterwards, run:
+
+    ./gradlew publishToMavenLocal
+
+to build the plugin artifacts and publish them locally to
+`~/.m2/repository/org/jetbrains/compose`.
+
+### Using the snapshot version plugin from Maven local
+
+In your project that uses Compose, make sure to have a `settings.gradle.kts`
+with plugin management configured to resolve from Maven local:
+
+```
+pluginManagement {
+    repositories {
+        mavenLocal()
+        gradlePluginPortal()
+    }
+}
+```
+
+Then, in your `build.gradle.kts` file, use the snapshot version:
+
+    id("org.jetbrains.compose") version "1.2.0-SNAPSHOT"