Add .editorconfig file

Default to LF EOL, UTF-8 and space indent. 4 space indent for .py/.sh files.

See https://editorconfig.org/

based on https://github.com/Electron-Cash/Electron-Cash/commit/de392bb92c9aa8a3ab46a56334a90b8159d8fddc

.editorconfig

@@ -0,0 +1,17 @@
+# see https://EditorConfig.org
+
+root = true
+
+[*]
+indent_style = space
+trim_trailing_whitespace = true
+end_of_line = lf
+charset = utf-8
+
+[*.py]
+indent_size = 4
+insert_final_newline = true
+
+[*.sh]
+indent_size = 4
+insert_final_newline = true