Simd128 vec-dot for q4_0. (#974)

* Simd128 vec-dot for q4_0.

* Bugfix.

* Add wasm tests.

* Bugfix for the q40 vecdot.

* More quantization tests.

candle-wasm-tests/src/lib.rs

@@ -0,0 +1,14 @@
+pub fn add(left: usize, right: usize) -> usize {
+    left + right
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn it_works() {
+        let result = add(2, 2);
+        assert_eq!(result, 4);
+    }
+}