examples don't build with default features

[0xalpharush]

The example in the README and in the rust doc comments don't build with the default features of the library. It is necessary to add
features like foundry-compilers = {git = "https://github.com/foundry-rs/compilers/" , ref ="850de5063f280046dd0e06ea9176700f08650fb5", features = ["project-util", "svm-solc"]}

Tests with similar code are guarded by these, for example.

compilers/crates/compilers/src/compile/project.rs

Lines 557 to 559 in b04423c

	#[cfg(all(feature = "project-util", feature = "svm-solc"))]
	mod tests {
	use std::path::Path;

The build error:

error[E0277]: the trait bound `MultiCompiler: std::default::Default` is not satisfied
 --> src/main.rs:7:12
  |
7 |     .build(Default::default())
  |            ^^^^^^^^^^^^^^^^^^ the trait `std::default::Default` is not implemented for `MultiCompiler`