replacing u32 -> string in adder tutorial example

[dmk978]

Let's try mentioned example for use with string, that's absolute straightforward. Component compiles well, but issuing

wasm-tools component wit target/wasm32-wasip1/release/adder.wasm

command produce really big file filled with a lot of imports and references to standard WASI worlds:

package root:component;

world root {
  import wasi:cli/environment@0.2.0;
  import wasi:cli/exit@0.2.0;
  import wasi:io/error@0.2.0;
  import wasi:io/streams@0.2.0;
  import wasi:cli/stdin@0.2.0;
  import wasi:cli/stdout@0.2.0;
  import wasi:cli/stderr@0.2.0;
  import wasi:clocks/wall-clock@0.2.0;
  import wasi:filesystem/types@0.2.0;
  import wasi:filesystem/preopens@0.2.0;

  export docs:adder/add@0.1.0;
}

and that continues for several screens. Why?