feat: html reference and completition support

src/main/java/de/marhali/easyi18n/assistance/completion/XmlCompletionContributor.java

@@ -0,0 +1,17 @@
+package de.marhali.easyi18n.assistance.completion;
+
+import com.intellij.codeInsight.completion.CompletionContributor;
+import com.intellij.codeInsight.completion.CompletionType;
+import com.intellij.patterns.PlatformPatterns;
+import com.intellij.psi.impl.source.xml.XmlAttributeValueImpl;
+
+/**
+ * Xml specific completion contributor.
+ * @author adeptius
+ */
+public class XmlCompletionContributor extends CompletionContributor {
+    public XmlCompletionContributor() {
+        extend(CompletionType.BASIC, PlatformPatterns.psiElement().inside(XmlAttributeValueImpl.class),
+                new KeyCompletionProvider());
+    }
+}

src/main/java/de/marhali/easyi18n/assistance/reference/XmlKeyReferenceContributor.java

@@ -0,0 +1,38 @@
+package de.marhali.easyi18n.assistance.reference;
+
+import com.intellij.openapi.project.Project;
+import com.intellij.patterns.PlatformPatterns;
+import com.intellij.psi.PsiElement;
+import com.intellij.psi.PsiReference;
+import com.intellij.psi.PsiReferenceProvider;
+import com.intellij.psi.PsiReferenceRegistrar;
+import com.intellij.psi.impl.source.xml.XmlAttributeValueImpl;
+import com.intellij.util.ProcessingContext;
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * Xml specific key reference binding
+ * @author adeptius
+ */
+public class XmlKeyReferenceContributor extends AbstractKeyReferenceContributor {
+    @Override
+    public void registerReferenceProviders(@NotNull PsiReferenceRegistrar registrar) {
+        registrar.registerReferenceProvider(
+                PlatformPatterns.psiElement(XmlAttributeValueImpl.class),
+                getProvider());
+    }
+
+    private PsiReferenceProvider getProvider() {
+        return new PsiReferenceProvider() {
+            @Override
+            public PsiReference @NotNull [] getReferencesByElement(
+                    @NotNull PsiElement element, @NotNull ProcessingContext context) {
+
+                Project project = element.getProject();
+                XmlAttributeValueImpl literalExpression = (XmlAttributeValueImpl) element;
+                String value = literalExpression.getValue();
+                return getReferences(project, element, value);
+            }
+        };
+    }
+}

src/main/resources/META-INF/de.marhali.easyi18n-xml.xml

@@ -1,5 +1,11 @@
 <idea-plugin>
     <extensions defaultExtensionNs="com.intellij">
+
+        <psi.referenceContributor
+                language="HTML"
+                implementation="de.marhali.easyi18n.assistance.reference.XmlKeyReferenceContributor"
+        />
+
         <lang.foldingBuilder
                 language="HTML"
                 implementationClass="de.marhali.easyi18n.assistance.folding.XmlFoldingBuilder"
@@ -9,5 +15,11 @@
                 language="HTML"
                 implementationClass="de.marhali.easyi18n.assistance.documentation.CommonDocumentationProvider"
         />
+
+        <completion.contributor
+                language="HTML"
+                implementationClass="de.marhali.easyi18n.assistance.completion.XmlCompletionContributor"
+        />
+
     </extensions>
 </idea-plugin>