chore: update version to v2.0.0 in main.go

To make `go install` happy :-|

go.mod

@@ -1,4 +1,4 @@
-module git.donadeo.net/pdonadeo/todotxt2remind
+module git.donadeo.net/pdonadeo/todotxt2remind/v2
 
 go 1.24.1
 

main.go

@@ -6,7 +6,7 @@ import (
 	"io"
 	"os"
 
-	"git.donadeo.net/pdonadeo/todotxt2remind/internal/parser"
+	"git.donadeo.net/pdonadeo/todotxt2remind/v2/internal/parser"
 	"github.com/spf13/cobra"
 )
 
@@ -14,7 +14,7 @@ var (
 	inputFile  string
 	outputFile string
 	debug      bool
-	version    = "v2"
+	version    = "v2.0.0"
 )
 
 func main() {