ci: Add iota-mixing lint (#4532)

https://github.com/AdminBenni/iota-mixing

.golangci.yml

@@ -23,6 +23,7 @@ linters:
     - gosec
     - govet
     - ineffassign
+    - iotamixing
     - loggercheck
     # Check for simple misspellings of words. 
     - misspell