Use package.exclude to remove CI related files & examples

[42triangles]

This reduces the package size by:

	before	after	percentage change
uncompressed	62.1KiB	44.5KiB	-28.3%
compressed	17.8KiB	13.7KiB	-23.0%

Based on the current download numbers of version 0.14.7+wasi-0.2.4 since release, this equates to 7.4GiB/month less for downloading the compressed crate.

[alexcrichton]

Thanks! Do you know if the packaged version still works after examples are excluded? The [[example]] directives in Cargo.toml would then all be missing so I'm not sure if that works

[42triangles]

I'm sorry, I should've actually been more clear about that in the PR description, but I ended up forgetting.

To answer the question, yes, the packaged version still works, but during packaging there would be a warning for each then missing example (for reference: the documentation for package.exclude/package.include actually includes the exclusion of an example).

The example would not be available for crater runs or on docs.rs though, when they're not included.

[alexcrichton]

Ok sounds good!