Use binary mdbook rather than compiling

Author: davidcole1340

.github/workflows/docs.yml

@@ -34,10 +34,9 @@ jobs:
           version: ${{ matrix.llvm }}
           directory: ${{ runner.temp }}/llvm-${{ matrix.llvm }}
       - name: Install mdbook
-        uses: actions-rs/install@v0.1
+        uses: peaceiris/actions-mdbook@v1
         with:
-          crate: mdbook
-          version: latest
+          mdbook-version: latest
       - name: Build docs
         uses: actions-rs/cargo@v1
         env: