Add a readme that explains how to use the pde reusable osgi components

ui/org.eclipse.pde.bnd.ui/README.MD

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+# OSGi Reusable Components for bndlib
+
+The [bndlib](https://github.com/bndtools/bnd) offers various ways to build better OSGi bundles, this is used in
+
+- felix-bundle-plugin
+- bnd-maven-plugin
+- Tycho
+-  bndtools
+- PDE itself
+- ...
+
+This plugin offers a set of reusable UI components for these usecase to be integrated with Eclipse IDE in a way that is not specific to a given tooling (e.g. PDE, bndtools, m2e, ...)
+and therefore can be shared across these to prevent duplicate efforts, see [here](https://bnd.discourse.group/t/announcement-bnd-and-pde-cooperation/372) for more details.
+
+## General concepts for integration
+
+One problem for such a reusable component is that it usually needs to get holds of some objects in an specific way that is specific to a given tooling.
+To mitigate we use the [Eclipse Adapter Pattern](https://www.eclipse.org/articles/Article-Adapters/) as it is widely used in Eclipse, flexible and allows
+the use of [OSGi services / Dependency Injection](https://eclipse.dev/eclipse/news/4.18/platform_isv.php#dialog-adapterfactory-as-service) already.
+
+### The IProject adapter
+
+Components need to learn the project and workspace of a bndlib backed project, for this the very first step for an integration is to provide an adapter that can
+transform an (Eclipse) `IProject` into a (bndlib) `Project` (from were the Workspace then can be derived), an example might look like this:
+
+```
+@Component
+@AdapterTypes(adaptableClass = IProject.class, adapterNames = Project.class)
+public class BndPluginAdapter implements IAdapterFactory {
+
+  @Override
+  public <T> T getAdapter(Object adaptableObject, Class<T> adapterType) {
+    if (adaptableObject instanceof IProject eclipseProject) {
+      if (adapterType == Project.class) {
+        //... here we need to determine if the project is managed by our tooling, e.g. it is a PDE, Bndtool, Maven, ... backed project
+        if (/*... is relevant ... */) {
+          // if that is the case, setup a Project that represent your tooling specific setup and return it
+          Project bndProject = ... fetch or setup a project that maps to the given eclipse project...
+          return adapterType.cast(bndProject);
+        }
+      }
+    }
+    return null;
+  }
+
+}
+```
+
+## Available components
+
+Beside some integration stuff (e.g. enable to [discover bndlib plugins](https://github.com/eclipse-pde/eclipse.pde/blob/master/ui/org.eclipse.pde.bnd.ui/src/org/eclipse/pde/bnd/ui/internal/Auxiliary.java) inside an OSGi runtime)
+it currently offers these components:
+
+- [bnd templates](https://eclipse.dev/eclipse/news/4.31/pde.php#bndtemplates)
+- [osgi repositories view](https://eclipse.dev/eclipse/news/4.32/pde.php#osgirepositories)
+- Formating of bnd files, quick fixes, completion proposals
+- ... more to come ...