dev: Add .editorconfig for consistent file formatting

.editorconfig

@@ -0,0 +1,34 @@
+# this file helps keeping consistent code style in all the project. IDEs will
+# automatically use the code style as defined in this file
+# see https://editorconfig.org/
+root=true
+# Unix-style newlines with a newline ending every file
+[*]
+end_of_line=lf
+insert_final_newline=true
+charset=utf-8
+trim_trailing_whitespace=true
+
+[*.vala]
+indent_style=space
+indent_size=4
+
+[*.xml]
+indent_style=space
+indent_size=2
+
+[*.css]
+indent_style=space
+indent_size=2
+
+[*.json]
+indent_style=space
+indent_size=4
+
+[meson.build]
+indent_style=space
+indent_size=2
+
+[.gitlab-ci.yml]
+indent_style=space
+indent_size=2