Commit stack.yaml.lock into the repository

There is a long discussion in commercialhaskell/stack/issues/4795
about whether this should be done or not (especially see comments in
Jan 2020), but for a single-user like me where hpack version is
stable, committing this to the repo saves 2½ minutes of the total CI
build time, which is currently dominating (total time: 4m10s). So it
is definitely worth doing…

.github/workflows/ci.yml

@@ -14,12 +14,6 @@ jobs:
           enable-stack: true
           stack-version: 'latest'
 
-      - name: Generate stack.yaml.lock
-        run: |
-          stack --no-terminal ls snapshots
-          echo
-          test -f stack.yaml.lock
-
       - name: Cache Haskell dependencies
         uses: actions/cache@v2
         with:

.gitignore

@@ -15,7 +15,6 @@
 .hsenv*
 cabal-dev/
 /.stack-*/
-/stack.yaml.lock
 yesod-devel/
 /db/
 /site/

stack.yaml.lock

@@ -0,0 +1,19 @@
+# This file was autogenerated by Stack.
+# You should not edit this file by hand.
+# For more information, please see the documentation at:
+#   https://docs.haskellstack.org/en/stable/lock_files
+
+packages:
+- completed:
+    hackage: classy-prelude-yesod-1.5.0@sha256:8f7e183bdfd6d2ea9674284c4f285294ab086aff60d9be4e5d7d2f3c1a2b05b7,1330
+    pantry-tree:
+      size: 330
+      sha256: ae84d4cc0e1daf985db6cdcf2ac92319531b8e60f547183cc46480d00aafbe20
+  original:
+    hackage: classy-prelude-yesod-1.5.0@sha256:8f7e183bdfd6d2ea9674284c4f285294ab086aff60d9be4e5d7d2f3c1a2b05b7,1330
+snapshots:
+- completed:
+    size: 567675
+    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/17/13.yaml
+    sha256: 84fa3ab606af79b1239ec213e8db5d49e4857f461eda9ac61fe589c967643b7d
+  original: lts-17.13