feat: add buildmanual target, faker demo, subprocess examples, and contributing sidebar to manual

Add Makefile buildmanual target for manual generation and include faker_demo.wren, subprocess_async_demo.wren, subprocess_concurrent_demo.wren, and subprocess_fiber_demo.wren example scripts. Update manual sidebar across api pages to link new web-server tutorial and contributing section with module architecture, pure-wren/c-backed modules, foreign classes, async patterns, testing, and documentation pages.

test/web/client_batch.wren

@@ -0,0 +1,25 @@
+// retoor <retoor@molodetz.nl>
+
+import "scheduler" for Scheduler, Future
+
+var items = ["a", "b", "c"]
+
+var futures = []
+for (item in items) {
+    futures.add(async { "processed_" + item })
+}
+
+System.print(futures.count) // expect: 3
+System.print(futures[0] is Future) // expect: true
+System.print(futures[1] is Future) // expect: true
+System.print(futures[2] is Future) // expect: true
+
+var results = []
+for (f in futures) {
+    results.add(await f)
+}
+
+System.print(results.count) // expect: 3
+System.print(results[0]) // expect: processed_a
+System.print(results[1]) // expect: processed_b
+System.print(results[2]) // expect: processed_c

test/web/client_concurrent.wren

@@ -0,0 +1,24 @@
+// retoor <retoor@molodetz.nl>
+
+import "scheduler" for Scheduler, Future
+
+System.print("Creating futures") // expect: Creating futures
+
+var future1 = async { {"url": "url1", "status": 200} }
+var future2 = async { {"url": "url2", "status": 201} }
+var future3 = async { {"url": "url3", "status": 202} }
+
+System.print(future1 is Future) // expect: true
+System.print(future2 is Future) // expect: true
+System.print(future3 is Future) // expect: true
+
+var result1 = await future1
+var result2 = await future2
+var result3 = await future3
+
+System.print(result1["url"]) // expect: url1
+System.print(result1["status"]) // expect: 200
+System.print(result2["url"]) // expect: url2
+System.print(result2["status"]) // expect: 201
+System.print(result3["url"]) // expect: url3
+System.print(result3["status"]) // expect: 202

test/web/future_state.wren

@@ -0,0 +1,13 @@
+// retoor <retoor@molodetz.nl>
+
+import "scheduler" for Scheduler, Future
+
+var future = async { 42 }
+
+System.print(future is Future) // expect: true
+
+var result = await future
+
+System.print(result) // expect: 42
+System.print(future.isDone) // expect: true
+System.print(future.result) // expect: 42

test/web/websocket_response.wren

@@ -0,0 +1,12 @@
+// retoor <retoor@molodetz.nl>
+
+import "web" for WebSocketResponse
+
+var ws = WebSocketResponse.new()
+System.print(ws.isPrepared) // expect: false
+System.print(ws.isOpen) // expect: false
+
+var ws2 = WebSocketResponse.new()
+System.print(ws2 is WebSocketResponse) // expect: true
+System.print(ws2.isPrepared == false) // expect: true
+System.print(ws2.isOpen == false) // expect: true