feat: add local text (#44)

This commits extends the "add_local" function. It
adds support to take text and index/embed it.

embedchain/loaders/local_text.py

@@ -0,0 +1,10 @@
+class LocalTextLoader:
+
+    def load_data(self, content):
+        meta_data = {
+            "url": "local",
+        }
+        return [{
+            "content": content,
+            "meta_data": meta_data,
+        }]