Add the missing context argument in snippets for resolving partial names

[stof]

This argument is needed to be able to resolve partial names, as explained in the documentation around these snippets.
I currently wrote the snippet as if the $context was already defined by one of the snippets of the previous section. I think that the current wording makes it clear (the title of this section is Using the context for instance). An alternative would be to add a reminder about it:

$context = // ...
$typeResolver = new \phpDocumentor\Reflection\TypeResolver();
$type = $typeResolver->resolve('Types\Context', $context);

I also updated the link to the Composer website to use HTTPS (the site redirects to HTTPS anyway when accessing it with HTTP)

[mvriel]

Thanks! It would seem I had indeed forgot to add those in the README