Allow executing php files without installing additional php interpreter

[pronskiy]

Suggested by @marco-introini:

Something like "if the first parameter is not in phpup list of commands execute vendor/bin/php passing the argument". I don't know if it makes sense.
In this way, we can be up and running in very few steps:

phpup composer init
<add PHP version in composer.json>
phpup locus
<create my first PHP file>
phpup myFile.php (as an extra: maybe this can execute phpup locus if no PHP binary is found inside the vendor directory)

Better yet, maybe creating a new init command can reduce the effort:
phpup init
can: make composer init, add PHP version in composer.json, execute phpup locus

In this way to create a new project:

phpup init 8.3
<create myFile.php>
phpup myFile.php