[1/?] Add ability to run code examples in the playground: Move code samples to separate files (#544)

* top-level `/code-samples` directory
* flat structure within `/code-samples`
* file names within `/code-samples` having the page name, they are _primarily_ used in as a prefix
    * a few files only consist of said prefix
* file names consist of `[a-z-]`
* code samples are embedded, using the [snippet](https://squidfunk.github.io/mkdocs-material/reference/code-blocks/#embedding-external-files) feature with the two dashes each syntax (`--8<--`)
* code samples are reused when the same code is used elsewhere or lines from it ([snippet lines](https://facelessuser.github.io/pymdown-extensions/extensions/snippets/#snippet-lines) syntax). Code sample reuse, that could only be achieved by the [block format](https://facelessuser.github.io/pymdown-extensions/extensions/snippets/#block-format) is not done
* code samples currently have no new line at EOF
* we currently have code samples in the following languages:
    * pony (_see below_)
    * Bash (`.sh`; 13)
    * C (9)
    * Error (`.txt`; 3)

= 313 code samples, 298 unique snippets

Author: shaedrich

.gitignore

@@ -7,4 +7,7 @@
 /site
 
 # Caches and logs
-*.log
+*.log
+
+# vscode
+/.vscode

code-samples/actors-behaviors.pony

@@ -0,0 +1,9 @@
+actor Aardvark
+  let name: String
+  var _hunger_level: U64 = 0
+
+  new create(name': String) =>
+    name = name'
+
+  be eat(amount: U64) =>
+    _hunger_level = _hunger_level - amount.min(_hunger_level)

code-samples/actors-sequential.pony

@@ -0,0 +1,7 @@
+actor Main
+  new create(env: Env) =>
+    call_me_later(env)
+    env.out.print("This is printed first")
+
+  be call_me_later(env: Env) =>
+    env.out.print("This is printed last")

code-samples/aliasing-alias-types.pony

@@ -0,0 +1,2 @@
+fun test(a: A) =>
+  var b: A! = a

code-samples/aliasing-ephemeral-types.pony

@@ -0,0 +1,2 @@
+fun test(a: Wombat iso): Wombat iso^ =>
+  consume a

code-samples/aliasing-iso-to-tag.pony

@@ -0,0 +1,2 @@
+fun test(a: Wombat iso) =>
+  var b: Wombat tag = a // Allowed!

code-samples/aliasing-multiple-references-to-an-iso-object.pony

@@ -0,0 +1,2 @@
+fun test(a: Wombat iso) =>
+  var b: Wombat iso = a // Not allowed!

code-samples/aliasing-trn-to-box.pony

@@ -0,0 +1,2 @@
+fun test(a: Wombat trn) =>
+  var b: Wombat box = a // Allowed!

code-samples/appendices-annotations-empty-with-nosupertype-annotation.pony

@@ -0,0 +1,7 @@
+class \nosupertype\ Empty
+
+class Foo
+  fun foo[A: Any](a: (A | Empty val)) =>
+    match consume a
+    | let a': A => None
+    end

code-samples/appendices-annotations-empty-without-nosupertype-annotation.pony

@@ -0,0 +1,7 @@
+class Empty
+
+class Foo
+  fun foo[A: Any](a: (A | Empty val)) =>
+    match consume a
+    | let a': A => None
+    end