feat: add async/await keywords, Num/String extensions, and Jinja markdown example

Add `async` and `await` token support to the Wren compiler with scheduler resolution logic, extend `Num` with `e` constant, hyperbolic trig, base conversion, and new methods (`isZero`, `gcd`, `lcm`, `digits`, etc.), extend `String` with `lower`, `upper`, `capitalize`, `title`, and regenerate `wren_core.wren.inc`. Include `Makefile` for multi-platform builds, rewrite `README.md` with updated build instructions, and add `example/await_demo.wren` and `example/jinja_markdown.wren` demonstrating new features.

manual/getting-started/installation.html

@@ -40,6 +40,8 @@
                     <span class="section-title">API Reference</span>
                     <ul>
                         <li><a href="../api/index.html">Overview</a></li>
+                        <li><a href="../api/string.html">String</a></li>
+                        <li><a href="../api/number.html">Num</a></li>
                         <li><a href="../api/http.html">http</a></li>
                         <li><a href="../api/websocket.html">websocket</a></li>
                         <li><a href="../api/tls.html">tls</a></li>
@@ -58,6 +60,7 @@
                         <li><a href="../api/datetime.html">datetime</a></li>
                         <li><a href="../api/timer.html">timer</a></li>
                         <li><a href="../api/io.html">io</a></li>
+                        <li><a href="../api/pathlib.html">pathlib</a></li>
                         <li><a href="../api/scheduler.html">scheduler</a></li>
                         <li><a href="../api/math.html">math</a></li>
                     </ul>
@@ -139,7 +142,7 @@ sudo apt-get install build-essential libssl-dev git python3</code></pre>
                 <h3>Build</h3>
                 <pre><code>git clone https://github.com/wren-lang/wren-cli.git
 cd wren-cli
-cd projects/make && make</code></pre>
+make build</code></pre>
 
                 <p>The binary will be created at <code>bin/wren_cli</code>.</p>
 
@@ -221,7 +224,7 @@ cd projects/make.bsd && gmake</code></pre>
                 <pre><code>bin/wren_cli --version</code></pre>
 
                 <p>Run the test suite:</p>
-                <pre><code>python3 util/test.py</code></pre>
+                <pre><code>make tests</code></pre>
 
                 <p>Start the REPL:</p>
                 <pre><code>bin/wren_cli</code></pre>
@@ -242,7 +245,7 @@ cd projects/make.bsd && gmake</code></pre>
                 <h3>Build Errors</h3>
                 <p>Try cleaning and rebuilding:</p>
                 <pre><code>make clean
-make</code></pre>
+make build</code></pre>
 
                 <h3>Test Failures</h3>
                 <p>Run a specific test module to isolate issues:</p>