build: Add .editorconfig

.editorconfig

@@ -0,0 +1,28 @@
+root = true
+
+[*]
+charset = utf-8
+end_of_line = lf
+indent_size = 2
+indent_style = space
+insert_final_newline = true
+max_line_length = 120
+tab_width = 2
+trim_trailing_whitespace = true
+
+[LICENSE]
+indent_size = unset
+
+[mkdocs.yaml]
+max_line_length = unset
+
+[WORKSPACE.bazel]
+max_line_length = unset
+
+[.bazelproject]
+indent_size = 2
+
+# Note that https://github.com/editorconfig-checker/editorconfig-checker
+# which https://github.com/editorconfig-checker/editorconfig-checker.python
+# uses does not understand e.g. [{*.yaml,*.yml}] but only single ones.
+