doc (book)[03/14]: "Getting Started" index: link "crate" to glossary entry

Author: salewski

src/doc/src/getting-started/index.md

@@ -1,6 +1,9 @@
 ## Getting Started
 
-To get started with Cargo, install Cargo (and Rust) and set up your first crate.
+To get started with Cargo, install Cargo (and Rust) and set up your first
+[*crate*][def-crate].
 
 * [Installation](installation.md)
 * [First steps with Cargo](first-steps.md)
+
+[def-crate]:  ../appendix/glossary.md#crate  '"crate" (glossary entry)'