Add migration to create an index on load_new_guix_revision_job_events

To speed up the rendering of the index page.

sqitch/deploy/index_on_load_new_guix_revision_job_events_job_id.sql

@@ -0,0 +1,7 @@
+-- Deploy guix-data-service:index_on_load_new_guix_revision_job_events_job_id to pg
+
+BEGIN;
+
+CREATE INDEX load_new_guix_revision_job_events_job_id ON load_new_guix_revision_job_events USING btree (job_id);
+
+COMMIT;