style: add .editorconfig [skip ci]

.editorconfig

@@ -0,0 +1,18 @@
+# EditorConfig configuration for trezor-firmware
+# https://EditorConfig.org
+
+# Top-most EditorConfig file
+root = true
+
+# Unix-style newlines with a newline ending every file, utf-8 charset
+[*]
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true
+charset = utf-8
+
+# Ignore diffs/patches
+[*.{diff,patch}]
+end_of_line = unset
+insert_final_newline = unset
+trim_trailing_whitespace = unset