Add GeoIP and GeoSite support for expr (#38)

* feat: copy something from hysteria/extras/outbounds/acl

* feat: add geoip and geosite support for expr

* refactor: geo matcher

* fix: typo

* refactor: geo matcher

* feat: expose config options to specify local geoip/geosite db files

* refactor: engine.Config should not contains geo

* feat: make geosite and geoip lazy downloaded

* chore: minor code improvement

* docs: add geoip/geosite usage

---------

Co-authored-by: Toby <tobyxdd@gmail.com>

go.mod

@@ -12,11 +12,14 @@ require (
 	github.com/mdlayher/netlink v1.6.0
 	github.com/spf13/cobra v1.8.0
 	github.com/spf13/viper v1.18.2
+	github.com/stretchr/testify v1.8.4
 	go.uber.org/zap v1.26.0
+	google.golang.org/protobuf v1.31.0
 	gopkg.in/yaml.v3 v3.0.1
 )
 
 require (
+	github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc // indirect
 	github.com/fsnotify/fsnotify v1.7.0 // indirect
 	github.com/google/go-cmp v0.5.9 // indirect
 	github.com/hashicorp/hcl v1.0.0 // indirect
@@ -26,6 +29,7 @@ require (
 	github.com/mdlayher/socket v0.1.1 // indirect
 	github.com/mitchellh/mapstructure v1.5.0 // indirect
 	github.com/pelletier/go-toml/v2 v2.1.0 // indirect
+	github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2 // indirect
 	github.com/sagikazarmark/locafero v0.4.0 // indirect
 	github.com/sagikazarmark/slog-shim v0.1.0 // indirect
 	github.com/sourcegraph/conc v0.3.0 // indirect