Add an example to Actix web examples repo

[hsluoyz]

We should add a Casbin example to: https://github.com/actix/examples

And list Casbin into their README.

[hsluoyz]

@GopherJ @PsiACE

[hsluoyz]

Someone on actix-web's Gitter is requesting this feature: https://gitter.im/actix/actix-web

[PsiACE]

@hsluoyz

Please check https://github.com/PsiACE/actix-casbin-example first.
If everything is OK, we can add it to actix-example or elsewhere.

[hsluoyz]

@GopherJ

[GopherJ]

@PsiACE Looks good to me, we can add different examples to show different features. Now we just start from: https://github.com/PsiACE/actix-casbin-example

Thanks for it.

[hsluoyz]

Please make PR to: https://github.com/actix/examples

[PsiACE]

See actix/examples#264, I just opened this pr.

[hsluoyz]

Good. Thanks.

Also a update from customer: https://gitter.im/actix/actix-web

[PsiACE]

He need an example of ACL model. I will update later.

[GopherJ]

@PsiACE Thanks!

[PsiACE]

@GopherJ

Please check https://github.com/PsiACE/casbin-examples/tree/actix_fileadapter_acl/actix_fileadapter_acl

I think this can be used as a simple example.

[PsiACE]

See actix/examples#264, I just opened this pr.

Done!

[hsluoyz]

Don't forget advertising it next time !

Like I did: actix/examples#267