feat: paste as mermaid if applicable (#8116)

packages/excalidraw/mermaid.ts

@@ -0,0 +1,32 @@
+/** heuristically checks whether the text may be a mermaid diagram definition */
+export const isMaybeMermaidDefinition = (text: string) => {
+  const chartTypes = [
+    "flowchart",
+    "sequenceDiagram",
+    "classDiagram",
+    "stateDiagram",
+    "stateDiagram-v2",
+    "erDiagram",
+    "journey",
+    "gantt",
+    "pie",
+    "quadrantChart",
+    "requirementDiagram",
+    "gitGraph",
+    "C4Context",
+    "mindmap",
+    "timeline",
+    "zenuml",
+    "sankey",
+    "xychart",
+    "block",
+  ];
+
+  const re = new RegExp(
+    `^(?:%%{.*?}%%[\\s\\n]*)?\\b${chartTypes
+      .map((x) => `${x}(-beta)?`)
+      .join("|")}\\b`,
+  );
+
+  return re.test(text.trim());
+};