add update command

go.mod

@@ -3,9 +3,12 @@ module beszel
 go 1.22.4
 
 require (
+	github.com/blang/semver v3.5.1+incompatible
 	github.com/labstack/echo/v5 v5.0.0-20230722203903-ec5b858dab61
 	github.com/pocketbase/dbx v1.10.1
 	github.com/pocketbase/pocketbase v0.22.16
+	github.com/rhysd/go-github-selfupdate v1.2.3
+	github.com/spf13/cobra v1.8.1
 	golang.org/x/crypto v0.24.0
 )
 
@@ -41,9 +44,12 @@ require (
 	github.com/goccy/go-json v0.10.3 // indirect
 	github.com/golang-jwt/jwt/v4 v4.5.0 // indirect
 	github.com/golang/groupcache v0.0.0-20210331224755-41bb18bfe9da // indirect
+	github.com/google/go-github/v30 v30.1.0 // indirect
+	github.com/google/go-querystring v1.0.0 // indirect
 	github.com/google/uuid v1.6.0 // indirect
 	github.com/googleapis/gax-go/v2 v2.12.5 // indirect
 	github.com/hashicorp/golang-lru/v2 v2.0.7 // indirect
+	github.com/inconshreveable/go-update v0.0.0-20160112193335-8152e7eb6ccf // indirect
 	github.com/inconshreveable/mousetrap v1.1.0 // indirect
 	github.com/jmespath/go-jmespath v0.4.0 // indirect
 	github.com/kballard/go-shellquote v0.0.0-20180428030007-95032a82bc51 // indirect
@@ -54,8 +60,9 @@ require (
 	github.com/ncruces/go-strftime v0.1.9 // indirect
 	github.com/remyoudompheng/bigfft v0.0.0-20230129092748-24d4a6f8daec // indirect
 	github.com/spf13/cast v1.6.0 // indirect
-	github.com/spf13/cobra v1.8.1 // indirect
 	github.com/spf13/pflag v1.0.5 // indirect
+	github.com/tcnksm/go-gitconfig v0.1.2 // indirect
+	github.com/ulikunitz/xz v0.5.9 // indirect
 	github.com/valyala/bytebufferpool v1.0.0 // indirect
 	github.com/valyala/fasttemplate v1.2.2 // indirect
 	go.opencensus.io v0.24.0 // indirect