Add article and tutorial about Navigation Bar

* add docs about navigation bar for Custom Language Support topic
* add info in `topics/intro/content_updates.md`
* renumber articles after the added tutorial
* add `custom_language_tutorial_header` to `structure_aware_navbar.md`

simple_language_plugin/src/main/java/org/intellij/sdk/language/SimpleStructureAwareNavbar.java

@@ -0,0 +1,44 @@
+// Copyright 2000-2022 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
+
+package org.intellij.sdk.language;
+
+import com.intellij.icons.AllIcons;
+import com.intellij.ide.navigationToolbar.StructureAwareNavBarModelExtension;
+import com.intellij.lang.Language;
+import org.intellij.sdk.language.psi.SimpleFile;
+import org.intellij.sdk.language.psi.SimpleProperty;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import javax.swing.Icon;
+
+public class SimpleStructureAwareNavbar extends StructureAwareNavBarModelExtension {
+    @NotNull
+    @Override
+    protected Language getLanguage() {
+        return SimpleLanguage.INSTANCE;
+    }
+
+    @Override
+    public @Nullable String getPresentableText(Object object) {
+        if (object instanceof SimpleFile) {
+            return ((SimpleFile) object).getName();
+        }
+        if (object instanceof SimpleProperty) {
+            return ((SimpleProperty) object).getName();
+        }
+
+        return null;
+    }
+
+    @Override
+    @Nullable
+    public Icon getIcon(Object object) {
+        if (object instanceof SimpleProperty) {
+            return AllIcons.Nodes.Property;
+        }
+
+        return null;
+    }
+
+}

simple_language_plugin/src/main/java/org/intellij/sdk/language/SimpleStructureViewFactory.java

@@ -1,4 +1,4 @@
-// Copyright 2000-2022 JetBrains s.r.o. and other contributors. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+// Copyright 2000-2022 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
 
 package org.intellij.sdk.language;
 
@@ -20,7 +20,7 @@ public class SimpleStructureViewFactory implements PsiStructureViewFactory {
       @NotNull
       @Override
       public StructureViewModel createStructureViewModel(@Nullable Editor editor) {
-        return new SimpleStructureViewModel(psiFile);
+        return new SimpleStructureViewModel(editor, psiFile);
       }
     };
   }

simple_language_plugin/src/main/java/org/intellij/sdk/language/SimpleStructureViewModel.java

@@ -1,4 +1,4 @@
-// Copyright 2000-2022 JetBrains s.r.o. and other contributors. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+// Copyright 2000-2022 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
 
 package org.intellij.sdk.language;
 
@@ -6,15 +6,17 @@ import com.intellij.ide.structureView.StructureViewModel;
 import com.intellij.ide.structureView.StructureViewModelBase;
 import com.intellij.ide.structureView.StructureViewTreeElement;
 import com.intellij.ide.util.treeView.smartTree.Sorter;
+import com.intellij.openapi.editor.Editor;
 import com.intellij.psi.PsiFile;
 import org.intellij.sdk.language.psi.SimpleProperty;
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 public class SimpleStructureViewModel extends StructureViewModelBase implements
         StructureViewModel.ElementInfoProvider {
 
-  public SimpleStructureViewModel(PsiFile psiFile) {
-    super(psiFile, new SimpleStructureViewElement(psiFile));
+  public SimpleStructureViewModel(@Nullable Editor editor, PsiFile psiFile) {
+    super(psiFile, editor, new SimpleStructureViewElement(psiFile));
   }
 
   @NotNull
@@ -33,4 +35,8 @@ public class SimpleStructureViewModel extends StructureViewModelBase implements
     return element.getValue() instanceof SimpleProperty;
   }
 
+  @Override
+  protected Class<?> @NotNull [] getSuitableClasses() {
+    return new Class[]{SimpleProperty.class};
+  }
 }

simple_language_plugin/src/main/resources/META-INF/plugin.xml

@@ -63,6 +63,7 @@
     <gotoSymbolContributor implementation="org.intellij.sdk.language.SimpleChooseByNameContributor"/>
     <lang.psiStructureViewFactory language="Simple"
                                   implementationClass="org.intellij.sdk.language.SimpleStructureViewFactory"/>
+    <navbar implementation="org.intellij.sdk.language.SimpleStructureAwareNavbar"/>
     <lang.formatter language="Simple" implementationClass="org.intellij.sdk.language.SimpleFormattingModelBuilder"/>
     <codeStyleSettingsProvider implementation="org.intellij.sdk.language.SimpleCodeStyleSettingsProvider"/>
     <langCodeStyleSettingsProvider implementation="org.intellij.sdk.language.SimpleLanguageCodeStyleSettingsProvider"/>