Add editorconfig integration

.editorconfig:
Add editorconfig integration, that covers .py, .rst and .yml files.

.editorconfig

+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+# Top-most EditorConfig file
+root = true
+
+# Unix-style newlines without trailing whitespaces, but with a newline
+# ending every file, utf-8 charset, set indent to spaces with width of four
+[*.py]
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true
+charset = utf-8
+indent_style = space
+indent_size = 4
+max_line_length = 120
+
+[*.{yml,yaml}]
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true
+charset = utf-8
+indent_style = space
+indent_size = 2
+
+[*.rst]
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true
+charset = utf-8
+indent_style = space
+indent_size = 2