editorconfig: add .editorfile to support a consistent coding style

.editorconfig

@@ -0,0 +1,26 @@
+# EditorConfig is awesome: https://EditorConfig.org
+
+# top-most EditorConfig file
+root = true
+
+# Unix-style newlines with a newline ending every file
+[*]
+end_of_line = lf
+insert_final_newline = true
+
+[{**/*.cc,**/*.hpp,**/*.ah,**/*.ah.in}]
+indent_style = tab
+indent_size = 4
+
+[*.py]
+indent_style = space
+indent_size = 4
+
+[Makefile]
+indent_style = tab
+
+[CMakeLists.txt]
+indent_style = tab
+indent_size = 4
+
+