fix indention and add EditorConfig configuration

Signed-off-by: Christian Hesse <mail@eworm.de>

.editorconfig

@@ -0,0 +1,15 @@
+# EditorConfig configuration for archiso
+# http://EditorConfig.org
+
+# 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
+[*]
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true
+charset = utf-8
+indent_style = space
+indent_size = 4