Adds version command and Makefile for build info

Provides a `gitlocal version` command to display the application's version, commit hash, and build date.

Introduces a `Makefile` to automate builds, installations, and tests. The Makefile dynamically extracts version, commit, and date from git tags, commit hashes, and build timestamps, injecting this metadata into the Go binary via `ldflags`.

Updates the `README.md` to document the new command and recommended build process using the Makefile.

cmd/version.go

@@ -0,0 +1,31 @@
+package cmd
+
+import (
+	"fmt"
+
+	"github.com/spf13/cobra"
+)
+
+var (
+	// Version is set via -ldflags during build
+	Version = "dev"
+	// Commit is set via -ldflags during build
+	Commit = "unknown"
+	// Date is set via -ldflags during build
+	Date = "unknown"
+)
+
+var versionCmd = &cobra.Command{
+	Use:   "version",
+	Short: "Print version information",
+	Long:  `Display the version, commit hash, and build date of gitlocal.`,
+	Run: func(cmd *cobra.Command, args []string) {
+		fmt.Printf("gitlocal version %s\n", Version)
+		fmt.Printf("  Commit: %s\n", Commit)
+		fmt.Printf("  Built:  %s\n", Date)
+	},
+}
+
+func init() {
+	rootCmd.AddCommand(versionCmd)
+}