Update Rust example with clear identifiers

[jordithijsman]

Currently the Rust example often uses the same name for packages, functions, worlds, interfaces. (This might also be the case elsewhere in the book, not sure)

Example:

component-docs/component-model/src/language-support/rust.md

Lines 82 to 92 in 31445f3

	```wit
	package docs:adder@0.1.0;
	interface add {
	add: func(a: u32, b: u32) -> u32;
	}
	world adder {
	export add;
	}
	```

Here the package name is the same as the world name and the interface name is the same as the function name. Once you start using it elsewhere in the example it can be very unclear if you refer to the package, world, interface,... While this works fine for someone who is just copy pasting the example, true understanding requires one to know where to reference what exactly. This example is very hard to extrapolate to other components and projects.

I would propose that the examples clearly label everything e.g., adder-package, adder-world,...

If other people agree I could create a pull-request for this.