Fix benchmarking CI job

.github/workflows/benchmark.yml

@@ -1,20 +1,13 @@
 name: Benchmark
 on:
   - pull_request
+permissions:
+  pull-requests: write    # needed to post comments
 jobs:
   benchmark:
     name: Benchmark
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
-      - uses: julia-actions/setup-julia@v1
+      - uses: MilesCranmer/AirspeedVelocity.jl@action-v1
         with:
-          version: '1'
-      - run: git fetch origin '+refs/heads/master:refs/remotes/origin/master'
-      - run: git branch master origin/master
-      - run: |
-          julia --project=benchmark -e '
-            using Pkg
-            Pkg.develop(PackageSpec(path=pwd()))
-            Pkg.instantiate()'
-      - run: julia --project=benchmark benchmark/runbenchmarks.jl
+          julia-version: '1'