add .editorconfig file, mainly to specify that tabs shall be used

See https://editorconfig.org/ for details on the file format.

.editorconfig

@@ -0,0 +1,13 @@
+# this is the top-most EditorConfig file
+root = true
+
+[*]
+# Unix-style newlines, with a newline ending the file
+end_of_line = lf
+insert_final_newline = true
+
+charset = utf-8
+
+[*.zone]
+indent_style = tab
+indent_size = 8

README.md

@@ -4,6 +4,8 @@
 If you make changes to any zone file, you must change the `Serial` value (at the top of the file) to a higher value, so that the changes will actually be used.
 Use the current date followed followed by `01` (or a higher number) as the new serial number.
 
+Also, please use tabs (instead of spaces) for consistent formatting.
+
 ## Applying Changes
 To actually activate any changes, someone with admin access needs to
 * make sure the changes are contained in the "dns" repository on the internal Git server