feat: sample diagram and docs for gitgraph

src/lib/components/preset.svelte

@@ -79,6 +79,18 @@
     section Go home
       Go downstairs: 5: Me
       Sit down: 3: Me
+      `,
+		'Git Graph': `    gitGraph
+      commit
+      commit
+      branch develop
+      checkout develop
+      commit
+      commit
+      checkout main
+      merge develop
+      commit
+      commit
 `
 	};
 

src/routes/edit.svelte

@@ -59,6 +59,10 @@
 		},
 		journey: {
 			code: '/#/user-journey'
+		},
+		gitGraph: {
+			code: '/#/gitgraph',
+			config: '/#/gitgraph?id=gitgraph-specific-configuration-options'
 		}
 	};
 	let text = '';