add solutions for [Package and Crate]

solutions/crate-module/crate.md

@@ -0,0 +1,43 @@
+1. `cargo new hello-package`
+
+2. `cargo new --lib hello-package1`
+
+3. `hello-package` has a binary crate named `hello-package`, `src/main.rs` is the crate root. 
+   
+`hello-pacakge1` has a library crate named `hello-package1`, `src/lib.rs` is the crate root.
+
+4. `hello-package1`
+
+5.
+```shell
+# FILL in the blanks
+.
+├── Cargo.lock
+├── Cargo.toml
+├── src
+│   ├── main.rs
+│   └── lib.rs
+```
+
+6.
+```shell
+# Create a package which contains 
+# 1. three binary crates: `hello-package`, `main1` and `main2`
+# 2. one library crate
+# describe the directory tree below
+.
+├── Cargo.toml
+├── Cargo.lock
+├── src
+│   ├── main.rs
+│   ├── lib.rs
+│   └── bin
+│       └── main1.rs
+│       └── main2.rs
+├── tests # directory for integrated tests files
+│   └── some_integration_tests.rs
+├── benches # dir for benchmark files
+│   └── simple_bench.rs
+└── examples # dir for example files
+    └── simple_example.rs
+```