Update V8 implementation status (#392)

Author: ngzhian

proposals/simd/ImplementationStatus.md

@@ -149,7 +149,7 @@
 | `i32x4.min_u`              |               `-msimd128` | :heavy_check_mark: |                    |                    | :heavy_check_mark: |
 | `i32x4.max_s`              |               `-msimd128` | :heavy_check_mark: |                    |                    | :heavy_check_mark: |
 | `i32x4.max_u`              |               `-msimd128` | :heavy_check_mark: |                    |                    | :heavy_check_mark: |
-| `i32x4.dot_i16x8_s`        |                           |                    |                    |                    |                    |
+| `i32x4.dot_i16x8_s`        |                           | :heavy_check_mark: |                    |                    |                    |
 | `i64x2.neg`                |               `-msimd128` | :heavy_check_mark: |                    |                    | :heavy_check_mark: |
 | `i64x2.shl`                |               `-msimd128` | :heavy_check_mark: |                    |                    | :heavy_check_mark: |
 | `i64x2.shr_s`              |               `-msimd128` | :heavy_check_mark: |                    |                    | :heavy_check_mark: |
@@ -191,12 +191,12 @@
 | `i32x4.trunc_sat_f32x4_u`  |               `-msimd128` | :heavy_check_mark: |                    |                    | :heavy_check_mark: |
 | `f32x4.convert_i32x4_s`    |               `-msimd128` | :heavy_check_mark: |                    |                    | :heavy_check_mark: |
 | `f32x4.convert_i32x4_u`    |               `-msimd128` | :heavy_check_mark: |                    |                    | :heavy_check_mark: |
-| `v128.load32_zero`         |                           |                    |                    |                    |                    |
-| `v128.load64_zero`         |                           |                    |                    |                    |                    |
+| `v128.load32_zero`         |                           | :heavy_check_mark: |                    |                    |                    |
+| `v128.load64_zero`         |                           | :heavy_check_mark: |                    |                    |                    |
 
 [1] Tip of tree LLVM as of May 20, 2020
 
-[2] V8 8.7.153. Requires flag `--experimental-wasm-simd`
+[2] V8 8.8.218. Requires flag `--experimental-wasm-simd`
 
 [3] Not known to be updated after latest renumbering. Requires flag `--enable simd`