Add egglog to the CI so we stop breaking it

Author: pavpanchekha

.github/workflows/unit-test.yml

@@ -57,6 +57,10 @@ jobs:
           racket -l herbie report --threads yes --seed 1 bench/hamming/rearrangement.fpcore graphs0
           racket -l herbie report --threads yes --seed 1 bench/hamming/rearrangement.fpcore graphs1
           racket infra/diff.rkt graphs0 graphs1
+      - name: "Test the egglog backend"
+        run: |
+          racket -l herbie improve --enable generate:egglog --seed 1 bench/tutorial.fpcore /tmp/out.fpcore
+          test `grep -c :precision /tmp/out.fpcore` -eq 3
       - name: "Run Herbie with egglog"
         run: racket -l herbie report --timeout 600 +o generate:egglog --seed 1 bench/hamming/trigonometry.fpcore graphs2