Fix the GPGPU example (#83)

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@@ -59,7 +59,7 @@
         <form>
           <textarea id="code">export fn main {
   // Create a buffer of memory on the GPU
-  let b = GBuffer([1, 2, 3, 4]);
+  let b = GBuffer([1.i32, 2.i32, 3.i32, 4.i32]);
   // Map the values into a new buffer on the GPU
   let out = b.map(fn (val: gi32) = val + 2);
   // Read the results back to RAM and print them