reduce frequency of scala-steward to 30 days

Author: hrj

.github/scala-steward.conf

@@ -1,3 +1,33 @@
 # If true, Scala Steward will sign off all commits (e.g. `git --signoff`).
 # Default: false
 signoffCommits = true
+
+
+# pullRequests.frequency allows to control how often or when Scala Steward
+# is allowed to create pull requests.
+#
+# Possible values:
+#   @asap
+#     PRs are created without delay.
+#
+#   <timespan>
+#     PRs are created only again after the given timespan since the last PR
+#     has passed. Example values are "36 hours", "1 day", or "14 days".
+
+#   <CRON expression>
+#     PRs are created roughly according to the given CRON expression.
+#
+#     CRON expressions consist of five fields:
+#     minutes, hour of day, day of month, month, and day of week.
+#
+#     See https://www.alonsodomin.me/cron4s/userguide/index.html#parsing for
+#     more information about the CRON expressions that are supported.
+#
+#     Note that the date parts of the CRON expression are matched exactly
+#     while the time parts are only used to abide to the frequency of
+#     the given expression.
+#
+# Default: "@asap"
+#
+#pullRequests.frequency = "0 0 ? * 3" # every thursday on midnight
+pullRequests.frequency = "30 days"