Add cmd/datdump/main.go (#3213)

* Feat: add a new datdump tool

* Refactor: address code review comments

* Refactor: remove export all from main program

use datdump instead

* Refactor: allow spaces in exportlists

e.g. `--exportlists="lista, listb"`

* all: cleanup

* apply review suggestion

---------

Co-authored-by: database64128 <free122448@hotmail.com>

internal/dlc/dlc.go

@@ -0,0 +1,9 @@
+package dlc
+
+const (
+	RuleTypeDomain     string = "domain"
+	RuleTypeFullDomain string = "full"
+	RuleTypeKeyword    string = "keyword"
+	RuleTypeRegexp     string = "regexp"
+	RuleTypeInclude    string = "include"
+)