Ajout d'un editorconfig file

cf https://editorconfig.org

.editorconfig

@@ -0,0 +1,21 @@
+root = true
+
+[*]
+end_of_line = lf
+trim_trailing_whitespace = true
+charset = utf-8
+
+[*.{html,css,js}]
+indent_style = space
+indent_size = 2
+
+[*.{yml,yaml}]
+indent_style = space
+indent_size = 2
+
+[*.json]
+indent_style = space
+indent_size = 2
+
+[*.md]
+trim_trailing_whitespace = false