doc: add some initial docs about this POM

README.md

@@ -1,2 +1,28 @@
 # maven-parent
-A common Maven Parent for all GDCC and IQSS Java projects
+
+A common Maven Parent for all GDCC and IQSS Java projects:
+
+```xml
+<parent>
+    <groupId>io.gdcc</groupId>
+    <artifactId>parent</artifactId>
+    <version>x.y.z</version>
+</parent>
+```
+
+## Important variables
+
+| Maven Property | Description                                         |
+|----------------|-----------------------------------------------------|
+| `jdk.version`  | The minimum Java version a project can be used with |
+| `skipUT`       | Skip executing unit tests with Surefire             |
+| `skipIT`       | Skip executing integration tests with Failsafe      |
+
+(There are more, docs to be done)
+
+## Profiles
+
+| Maven Profile | Description                                      |
+|---------------|--------------------------------------------------|
+| `release`     | Prepare a package for releasing to Maven Central |
+| `coverage`    | Run JaCoCo, also contains some Sonar properties  |