Add isomorphic basename utility

packages/editor-ext/src/lib/markdown/utils/basename.ts

@@ -0,0 +1,29 @@
+/**
+ * Flexible `basename` implementation for node and the browser
+ * @see https://stackoverflow.com/a/59907288/2228771
+ */
+export function getBasename(path: string) {
+  // make sure the basename is not empty, if string ends with separator
+  let end = path.length - 1;
+  while (path[end] === '/' || path[end] === '\\') {
+    --end;
+  }
+
+  // support mixing of Win + Unix path separators
+  const i1 = path.lastIndexOf('/', end);
+  const i2 = path.lastIndexOf('\\', end);
+
+  let start: number;
+  if (i1 === -1) {
+    if (i2 === -1) {
+      // no separator in the whole thing
+      return path;
+    }
+    start = i2;
+  } else if (i2 === -1) {
+    start = i1;
+  } else {
+    start = Math.max(i1, i2);
+  }
+  return path.substring(start + 1, end + 1);
+}