add solution in Python for 0028_find_the_index_of_the_first_occurrence.py

Author: Saimon398

python_solutions/0028_find_the_index_of_the_first_occurrence.py

@@ -0,0 +1,6 @@
+def strStr(self, haystack: str, needle: str) -> int:
+  for i in range(len(haystack)):
+    if(haystack[i:len(needle) + i] == needle):
+      return i
+        
+  return -1