completion: Add bash-it doctor completion

Also fix the tests and add a new one

completion/available/bash-it.completion.bash

@@ -65,7 +65,7 @@ _bash-it-comp()
   prev="${COMP_WORDS[COMP_CWORD-1]}"
   chose_opt="${COMP_WORDS[1]}"
   file_type="${COMP_WORDS[2]}"
-  opts="disable enable help migrate reload search show update version"
+  opts="disable enable help migrate reload doctor search show update version"
   case "${chose_opt}" in
     show)
       local show_args="aliases completions plugins"
@@ -82,6 +82,11 @@ _bash-it-comp()
         return 0
       fi
       ;;
+    doctor)
+      local doctor_args="errors warnings all"
+      COMPREPLY=( $(compgen -W "${doctor_args}" -- ${cur}) )
+      return 0
+      ;;
     migrate | reload | search | update | version)
       return 0
       ;;