Merge pull request #15 from chevdor/will-editorconfig

Add same .editorconfig than Substrate

polkadot/.editorconfig

+root = true
+[*]
+indent_style=tab
+indent_size=tab
+tab_width=4
+end_of_line=lf
+charset=utf-8
+trim_trailing_whitespace=true
+max_line_length=120
+insert_final_newline=true
+
+[*.yml]
+indent_style=space
+indent_size=2
+tab_width=8
+end_of_line=lf