Add version output

[nitrocode]

It would be nice to add a version output.

The version seems to be passed in

hcl2json/.github/workflows/deploy.yml

Lines 47 to 58 in 75e097e

	- name: Update environment
	run: |
	echo "VERSION=${GITHUB_REF#refs/tags/v}" >> $GITHUB_ENV
	echo "TARGET_NAME=hcl2json_${{ matrix.os.name }}_${{ matrix.arch}}${{ matrix.os.ext }}" >> $GITHUB_ENV
	- name: Build
	run: 'go build -ldflags="-X main.Version=${{ env.VERSION }}"'
	- name: Upload
	env:
	GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
	run: |
	mv hcl2json${{ matrix.os.ext }} $TARGET_NAME
	gh release upload v$VERSION $TARGET_NAME

But not exposed as a flag

hcl2json/main.go

Lines 17 to 20 in 75e097e

	var options convert.Options
	flag.BoolVar(&options.Simplify, "simplify", false, "If true attempt to simply expressions which don't contain any variables or unknown functions")
	flag.Parse()

---

It could be as simple as this

import (
	"bytes"
	"encoding/json"
	"flag"
+	"fmt"
	"io"
	"log"
	"os"

	"github.com/tmccombs/hcl2json/convert"
)

+var (
+    version = "dev"
+)

func main() {
	logger := log.New(os.Stderr, "", 0)

	var options convert.Options

	flag.BoolVar(&options.Simplify, "simplify", false, "If true attempt to simply expressions which don't contain any variables or unknown functions")
+	flag.BoolVar(&options.Version, "version", false, "return version")
	flag.Parse()

+	if options.Version {
+		fmt.Println(options.Version)
+		os.Exit(0)
+	}