x/pkgsite: expose Postgres port to loopback

Expose the Postgres port to loopback so that it works under WSL, enabling the tests run by all.bash to complete successfully based on the setup instructions in doc/postgres.md.

Fixes golang/go#60009

Change-Id: I091d6db6319ac504c77279ada67c9a6e5a5bef84
GitHub-Last-Rev: 2dcf9d22deaa13cb6f2e567c6e2e2d699c1b8be0
GitHub-Pull-Request: golang/pkgsite#65
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/493076
Reviewed-by: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Result: kokoro <noreply+kokoro@google.com>
diff --git a/devtools/docker/compose.yaml b/devtools/docker/compose.yaml
index 7800a97..b54d88d 100644
--- a/devtools/docker/compose.yaml
+++ b/devtools/docker/compose.yaml
@@ -121,6 +121,8 @@
       POSTGRES_USER: ${GO_DISCOVERY_DATABASE_USER:-postgres}
     volumes:
       - pgdata:/var/lib/postgresql/data
+    ports:
+      - 127.0.0.1:5432:5432
   nodejs:
     image: node:14.17.0
     environment: