implement --version flag as alias to version command

## Problem
sem has the `version` command, however linux standard is --version flags for most commands.

## Expectation
```
sem --version
0.26.3, commit 2833b829ee1b8b0d516ef0deb5f68b124cca20dd, built at 2022-10-19T16:49:42Z
```

## Actual
```bash
$ sem --version
Error: unknown flag: --version
```