Add license files to published deadpool-* crates

[musicinmybrain]

Add symbolic links so that LICENSE-APACHE and LICENSE-MIT are included in all of the published deadpool-* crates, as required by the terms of the chosen licenses.

Before this PR:

$ gh repo clone bikeshedder/deadpool
$ cd deadpool/runtime
$ cargo publish --dry-run
$ tar -tzvf ../target/package/deadpool-runtime-0.1.3.crate
-rw-r--r-- 0/0             101 1969-12-31 19:00 deadpool-runtime-0.1.3/.cargo_vcs_info.json
-rw-r--r-- 0/0            1087 2006-07-23 21:21 deadpool-runtime-0.1.3/CHANGELOG.md
-rw-r--r-- 0/0            1087 1969-12-31 19:00 deadpool-runtime-0.1.3/Cargo.toml
-rw-r--r-- 0/0             704 2006-07-23 21:21 deadpool-runtime-0.1.3/Cargo.toml.orig
-rw-r--r-- 0/0            1486 2006-07-23 21:21 deadpool-runtime-0.1.3/README.md
-rw-r--r-- 0/0            4047 2006-07-23 21:21 deadpool-runtime-0.1.3/src/lib.rs

After this PR:

$ cargo publish --dry-run
$ tar -tzvf ../target/package/deadpool-runtime-0.1.3.crate
-rw-r--r-- 0/0             101 1969-12-31 19:00 deadpool-runtime-0.1.3/.cargo_vcs_info.json
-rw-r--r-- 0/0            1087 2006-07-23 21:21 deadpool-runtime-0.1.3/CHANGELOG.md
-rw-r--r-- 0/0            1087 1969-12-31 19:00 deadpool-runtime-0.1.3/Cargo.toml
-rw-r--r-- 0/0             704 2006-07-23 21:21 deadpool-runtime-0.1.3/Cargo.toml.orig
-rw-r--r-- 0/0           11346 2006-07-23 21:21 deadpool-runtime-0.1.3/LICENSE-APACHE
-rw-r--r-- 0/0            1083 2006-07-23 21:21 deadpool-runtime-0.1.3/LICENSE-MIT
-rw-r--r-- 0/0            1486 2006-07-23 21:21 deadpool-runtime-0.1.3/README.md
-rw-r--r-- 0/0            4047 2006-07-23 21:21 deadpool-runtime-0.1.3/src/lib.rs

Note that the symbolic links are resolved by cargo publish, and the resulting crates contain the license texts as regular files.

[bikeshedder]

Thanks a lot!

[bikeshedder]

I just released all deadpool crates which do now include the license files in the published crates. 👍

[musicinmybrain]

Awesome, thanks!