Add .editorconfig file

See https://editorconfig.org/.

Change-Id: I199ed6acc8f55361df477ed067517510b11faf2d
Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/recipes-py/+/5416575
Reviewed-by: Yiwei Zhang <yiwzhang@google.com>
Commit-Queue: Yiwei Zhang <yiwzhang@google.com>
Auto-Submit: Rob Mohr <mohrr@google.com>
diff --git a/.editorconfig b/.editorconfig
new file mode 100644
index 0000000..2491fdf
--- /dev/null
+++ b/.editorconfig
@@ -0,0 +1,3 @@
+[*.py]
+indent_style = space
+indent_size = 2