Add title support using YAML frontmatter

cypress/integration/rendering/classDiagram-v2.spec.js

@@ -496,4 +496,16 @@ describe('Class diagram V2', () => {
     );
     cy.get('svg');
   });
+
+  it('1433: should render a simple class with a title', () => {
+    imgSnapshotTest(
+      `---
+       title: simple class diagram
+       ---
+       classDiagram-v2
+       class Class10
+      `,
+      {}
+    );
+  });
 });

cypress/integration/rendering/erDiagram.spec.js

@@ -273,4 +273,17 @@ describe('Entity Relationship Diagram', () => {
     );
     cy.get('svg');
   });
+
+  it('1433: should render a simple ER diagram with a title', () => {
+    imgSnapshotTest(
+      `---
+       title: simple ER diagram
+       ---
+       erDiagram
+       CUSTOMER ||--o{ ORDER : places
+       ORDER ||--|{ LINE-ITEM : contains
+      `,
+      {}
+    );
+  });
 });

cypress/integration/rendering/flowchart-v2.spec.js

@@ -663,4 +663,15 @@ flowchart RL
       { htmlLabels: true, flowchart: { htmlLabels: true }, securityLevel: 'loose' }
     );
   });
+  it('1433: should render a titled flowchart with titleTopMargin set to 0', () => {
+    imgSnapshotTest(
+      `---
+      title: Simple flowchart
+      ---
+      flowchart TD
+      A --> B
+      `,
+      { titleTopMargin: 0 }
+    );
+  });
 });

cypress/integration/rendering/gitGraph.spec.js

@@ -322,4 +322,15 @@ describe('Git Graph diagram', () => {
       {}
     );
   });
+  it('1433: should render a simple gitgraph with a title', () => {
+    imgSnapshotTest(
+      `---
+      title: simple gitGraph
+      ---
+      gitGraph
+       commit
+      `,
+      {}
+    );
+  });
 });

cypress/integration/rendering/stateDiagram-v2.spec.js

@@ -559,4 +559,16 @@ stateDiagram-v2
       );
     });
   });
+  it('1433: should render a simple state diagram with a title', () => {
+    imgSnapshotTest(
+      `---
+       title: simple state diagram
+       ---
+       stateDiagram-v2
+       [*] --> State1
+       State1 --> [*]
+      `,
+      {}
+    );
+  });
 });