fixup! README: Format "Targets" table.

Author: har7an

README.md

@@ -260,15 +260,21 @@ terminate.
     error `assertion failed: signal(libc::SIGPIPE, libc::SIG_IGN) !=
     libc::SIG_ERR`, see [issue
     #140](https://github.com/cross-rs/cross/issues/140) for more information.
+
 [2] No `std` component available.
+
 [3] For some \*BSD and Solaris targets, the libc column indicates the OS
     release version from which libc was extracted.
+
 [4] libc = newlib
+
 [5] Must change `image =
     "ghcr.io/cross-rs/x86_64-unknown-linux-gnu:main-centos"` in `Cross.toml`
     for `[target.x86_64-unknown-linux-gnu]` to use the CentOS7-compatible
     target.
+
 [6] libc = emscripten and GCC = clang
+
 [7] Must change `image =
     "ghcr.io/cross-rs/aarch64-unknown-linux-gnu:main-centos"` in `Cross.toml`
     for `[target.aarch64-unknown-linux-gnu]` to use the CentOS7-compatible