setup rust stable

Sometimes the rust toolchain was not properly installed

this installs the rust toolchain before running cargo. Fixes errors about rustc
being out of date.

.github/workflows/ci.yml

@@ -52,7 +52,7 @@ jobs:
         uses: actions-rs/cargo@v1
         with:
           command: install
-          args: cargo-wasmer --verbose --debug --version '^0.4'
+          args: cargo-wasmer --verbose --debug --version '^0.4' --locked
       - name: Type Checking
         uses: actions-rs/cargo@v1
         with: