fix(lang/csharp): Revise C# language support section (#299)

* Revise C# language support section

Added more details where necessary. Factored code examples out
into separate files and included them.

Fixed a bug where the package name in the Program.cs file
(in the "host-app" project) didn't match the package name in the .wit

Factored out duplicated text in "Run the component from the example
host" section that also appears in the C section; included this text
from separate .md files.

* Update component-model/src/language-support/csharp.md

Co-authored-by: Victor Adossi <123968127+vados-cosmonic@users.noreply.github.com>

* Put error message in code block

* Remove extra example

---------

Co-authored-by: Victor Adossi <123968127+vados-cosmonic@users.noreply.github.com>

Author: catamorphism

component-model/examples/tutorial/csharp/adder/Component.cs

@@ -0,0 +1,9 @@
+namespace ExampleWorld.wit.exports.docs.adder.v0_1_0;
+
+public class AddImpl : IAdd
+{
+    public static uint Add(uint x, uint y)
+    {
+        return x + y;
+    }
+}

component-model/examples/tutorial/csharp/adder/Program.cs

@@ -0,0 +1,8 @@
+// Pull in all imports of the `hostapp` world, namely the `add` interface.
+// example.component refers to the package name defined in the WIT file.
+using HostappWorld.wit.imports.docs.adder.v0_1_0;
+
+uint left = 1;
+uint right = 2;
+var result = AddInterop.Add(left, right);
+Console.WriteLine($"{left} + {right} = {result}");

component-model/examples/tutorial/csharp/adder/world-hostapp.wit

@@ -0,0 +1,13 @@
+package docs:adder@0.1.0;
+
+interface add {
+    add: func(x: u32, y: u32) -> u32;
+}
+
+world example {
+    export add;
+}
+
+world hostapp {
+    import add;
+}

component-model/src/language-support/c.md

@@ -321,56 +321,14 @@ The following section requires you to have [a Rust toolchain][rust] installed.
 > (The `wasmtime` version is specified in [the Cargo configuration file][cargo-config]
 > for the example host.)
 
-This repository contains an [example WebAssembly host][example-host] written in Rust
-that can run components that implement the `adder` world.
-
-1. `git clone https://github.com/bytecodealliance/component-docs.git`
-2. `cd component-docs/component-model/examples/example-host`
-3. `cargo run --release -- 1 2 <PATH>/adder.wasm`
-* The double dashes separate the flags passed to `cargo` from
-  the flags passed in to your code.
-* The arguments 1 and 2 are the arguments to the adder.
-* In place of `<PATH>`, substitute the directory that contains your
-  generated `adder.wasm` file (or `adder.component.wasm` if you used
-  the manual instructions).
-
-> [!NOTE]
-> When hosts run components that use WASI interfaces, they must *explicitly*
-> [add WASI to the linker][add-to-linker] to run the built component.
+{{#include example-host-part1.md}}
 
 A successful run should show the following output
 (of course, the paths to your example host and adder component will vary,
 and you should substitute `adder.wasm` with `adder.component.wasm`
 if you followed the manual instructions above):
 
-```
-cargo run --release -- 1 2 adder.wasm
-   Compiling example-host v0.1.0 (/path/to/component-docs/component-model/examples/example-host)
-    Finished `release` profile [optimized] target(s) in 7.85s
-     Running `target/debug/example-host 1 2 /path/to/adder.wasm`
-1 + 2 = 3
-```
-
-If *not* configured correctly, you may see errors like the following:
-
-```
-cargo run --release -- 1 2 adder.wasm
-   Compiling example-host v0.1.0 (/path/to/component-docs/component-model/examples/example-host)
-    Finished `release` profile [optimized] target(s) in 7.85s
-     Running `target/release/example-host 1 2 /path/to/adder.component.wasm`
-Error: Failed to instantiate the example world
-
-Caused by:
-    0: component imports instance `wasi:io/error@0.2.2`, but a matching implementation was not found in the linker
-    1: instance export `error` has the wrong type
-    2: resource implementation is missing
-```
-
-This kind of error normally indicates that the host in question does not satisfy WASI imports.
-
-[host]: https://github.com/bytecodealliance/component-docs/tree/main/component-model/examples/example-host
-[add-to-linker]: https://docs.wasmtime.dev/api/wasmtime_wasi/p2/fn.add_to_linker_sync.html
-[example-host]: https://github.com/bytecodealliance/component-docs/tree/main/component-model/examples/example-host
+{{#include example-host-part2.md}}
 
 ## 7. Run the component from C/C++ Applications