Add long LGTM: [Ll]ooks good to me approve regexp

Author: zbeekman

.pullapprove.yml

@@ -1,5 +1,5 @@
 approve_by_comment: true
-approve_regex: '^([Aa]pproved|:\+1:|:shipit:|:ship: it|LGTM|:zap:|:boom:|:clap:|:bow:)'
+approve_regex: '^([Aa]pproved|:\+1:|:shipit:|:ship: it|LGTM|[Ll]ooks good to me|:zap:|:boom:|:clap:|:bow:)'
 reject_regex: '^([Nn]ope|[Nn]ope\.jpg|[Dd]enied|[Rr]ejected|:\-1:)'
 reset_on_push: true
 author_approval: default