Add .editorconfig file to get right representation in gitea editor and view

.editorconfig

@@ -0,0 +1,13 @@
+# Top-most EditorConfig file
+root = true
+
+[*]
+indent_style = tab
+indent_size = 4
+end_of_file = lf
+charset = UTF-8
+trim_trailing_whitespace = true
+insert_final_newline = true
+
+[*.md]
+trim_trailing_whitespace = false