module: run go mod tidy && go mod vendor

vendor/github.com/btcsuite/btcd/btcjson/CONTRIBUTORS

@@ -0,0 +1,16 @@
+# This is the list of people who have contributed code to the repository.
+#
+# Names should be added to this file only after verifying that the individual
+# or the individual's organization has agreed to the LICENSE.
+#
+# Names should be added to this file like so:
+# Name <email address>
+
+John C. Vernaleo <jcv@conformal.com>
+Dave Collins <davec@conformal.com>
+Owain G. Ainsworth <oga@conformal.com>
+David Hill <dhill@conformal.com>
+Josh Rickmar <jrick@conformal.com>
+Andreas Metsälä <andreas.metsala@gmail.com>
+Francis Lam <flam@alum.mit.edu>
+Geert-Johan Riemer <geertjohan.riemer@gmail.com>