chore: add config for Publish to BCR app (#193)

Now that releases are automated, the release doesn't have an author, so
the app can't figure out whose fork of bazel-central-registry the PR
should originate from.

This will fix the error from publishing 6.0.0-rc0 to the BCR.
diff --git a/.bcr/config.yml b/.bcr/config.yml
new file mode 100644
index 0000000..9828ad2
--- /dev/null
+++ b/.bcr/config.yml
@@ -0,0 +1,3 @@
+fixedReleaser:
+  login: alexeagle
+  email: alex@aspect.dev