Make how to write dependencies acurate

[wataash]

Description

Prevent beginners from seeing build errors::

error[E0433]: failed to resolve: use of undeclared type or module `web_sys`
  --> src/lib.rs:24:21
   |
24 |         let window: web_sys::Window = web_sys::window().expect("window not available");
   |                     ^^^^^^^ use of undeclared type or module `web_sys`

or

error[E0433]: failed to resolve: use of undeclared type or module `stdweb`
  --> src/lib.rs:27:21
   |
27 |         let window: stdweb::web::Window = stdweb::web::window();
   |                     ^^^^^^ use of undeclared type or module `stdweb`

Checklist

• I have run cargo make pr-flow
• I have reviewed my own code
• I have added tests

[siku2]

These libraries aren't strictly required to use Yew so I'm not sure if we should really list them there.
New users might end up confused by this, as they're never using web-sys directly.
Maybe there's a better place to inform the user of these dependencies?

[wataash]

I see, but then should we remove or move ## Example Usage section?
Newbies would copy-paste these code without adding web-sys, and see the errors (at least I did).

[siku2]

stdweb will be gone soon anyway (#1569) so this entire section will hopefully be rewritten.
Not sure if it makes sense to take action because of that, but I'm fine with removing the example usage section. It doesn't even remotely paint the full picture.

[jstarry]

First, I think this whole section will go away when we phase out support for stdweb.

I personally think it's fine to have explicit dependencies on these libraries. Most apps will probably need to do so. Note that web-sys is re-exported by Yew though and can be accessed by yew::web_sys

[wataash]

Whoa, okay, so I close this PR and wait for the rewriting.

Thank you.

Note that web-sys is re-exported by Yew though and can be accessed by yew::web_sys

Good to hear that!