fix: template matching ignores casts

[Egor18]

Fix #3026.
I'm not so familiar with template matching in Spoon yet, but it looks like a bug to me.
I think matcher f(_x_.S()); should match f(new X()) as well as (Y) f(new X()), isn't it?

[monperrus]

Thanks a lot Egor for the bug reproduction.

Pavel @pvojtechovsky, we hope you're doing well. Any chance to have a look at this bug?

[Egor18]

I added a possible fix.
This is probably a bit arguable solution because we skip casts during template matching now, but on the other hand we already do that with comments and some other stuff.

[monperrus]

Thanks Egor, I like this solution. We just need to document it. Could you add the explanation in the corresponding Markdown file?

[monperrus]

added documentation, will merge after CI.

[monperrus]

thanks @Egor18