update README examples

[glibsm]

Need to take a pass. Includes things like:

err := dig.Resolve(&o) // notice the pointer to a pointer as param type
if err == nil {
    // o is ready to use
}

err = g.Resolve(&f1)
require.NoError(t, err)

[glibsm]

It would be ideal to illustrate an example of an actual graph. Something like:

Type1 -> Type2, Type3
Type2 -> Type4
Type3 -> Type5
Type4 -> Type6, Type7

Much like what's in the test, but a more realistic example.

[HelloGrayson]

I'll take this one 🥇

[glibsm]

Closing via #22
We can make further improvements as necessary (i still think some diagrams are helpful)