Add examples of linking and WASI (#1369)

* Add examples of linking and WASI

This commit adds two example programs, one for linking two modules
together and one for instantiating WASI. The linkage example
additionally uses WASI to get some meaningful output at this time.

cc #1272

* Add examples to the book as well

* More links!

* Ignore examples from rustdoc testsing

* More example updates

* More ignored

docs/SUMMARY.md

@@ -7,6 +7,22 @@
 - [Examples](./examples.md)
   - [Markdown parser](./examples-markdown.md)
   - [Profiling WebAssembly](./examples-profiling.md)
+  - [Embedding in Rust](./examples-rust-embed.md)
+    - [Hello, world!](./examples-rust-hello-world.md)
+    - [Calculating the GCD](./examples-rust-gcd.md)
+    - [Using linear memory](./examples-rust-memory.md)
+    - [WASI](./examples-rust-wasi.md)
+    - [Linking modules](./examples-rust-linking.md)
+    - [Debugging](./examples-rust-debugging.md)
+    - [Using multi-value](./examples-rust-multi-value.md)
+  - [Embedding in C](./examples-c-embed.md)
+    - [Hello, world!](./examples-c-hello-world.md)
+    - [Calculating the GCD](./examples-c-gcd.md)
+    - [Using linear memory](./examples-c-memory.md)
+    - [WASI](./examples-c-wasi.md)
+    - [Linking modules](./examples-c-linking.md)
+    - [Debugging](./examples-c-debugging.md)
+    - [Using multi-value](./examples-c-multi-value.md)
 - [Using WebAssembly from your lanugage](./lang.md)
   - [Python](./lang-python.md)
   - [.NET](./lang-dotnet.md)