Improve asset versioning task

[mcaskill]

Added:

• Support for writing multiple times to the same file to avoid conflicts between version tasks.
• Support for a hexadecimal value (using random bytes) instead of timestamp.

Changed:

• Task structure to decouple the version number generation from file handling to provide support for future unique IDs and hashes.

Regarding support for writing to the same file, one would generally only write a single version format. Just like before, there is still a risk of conflict if you are editing a file that might be being edited by another asynchronous task. For example, inserting the version number inside a CSS file that is generated by a Styles task.

Regarding using either a random hexadecimal value or a timestamp, it's more for personal preference.

Usage:

"versions": [
    {
        "format": "timestamp",
        "key": "now",
        "outfile": "./assets.json"
    },
    {
        "format": "hex:8",
        "key": "hex",
        "outfile": "./assets.json"
    }
]

{
    "now": 1665071717350,
    "hex": "6ef54181c4ba"
}