Fix usage of singular driver/ in CI jobs

One more similar to [1] (previous commit) that fixes the use of the
singular `driver/` in the GitHub workflows YAML file. Also take the
opportunity to rename `ci.yml` to `ci.yaml` so it has a longer quick
find target (one can type "yaml") and to match convention of Go and
Python.

[1] 9154108

Author: brandur

.github/workflows/ci.yml .github/workflows/ci.yaml.github/workflows/ci.yml renamed to .github/workflows/ci.yaml

@@ -35,11 +35,11 @@ jobs:
 
       - name: Build gem (riverqueue-activerecord)
         run: gem build riverqueue-activerecord.gemspec
-        working-directory: ./drivers/riverqueue-activerecord
+        working-directory: ./driver/riverqueue-activerecord
 
       - name: Build gem (riverqueue-sequel)
         run: gem build riverqueue-sequel.gemspec
-        working-directory: ./drivers/riverqueue-sequel
+        working-directory: ./driver/riverqueue-sequel
 
   lint:
     runs-on: ubuntu-latest
@@ -61,19 +61,19 @@ jobs:
 
       - name: bundle install (riverqueue-activerecord)
         run: bundle install
-        working-directory: ./drivers/riverqueue-activerecord
+        working-directory: ./driver/riverqueue-activerecord
 
       - name: Standard Ruby (riverqueue-activerecord)
         run: bundle exec standardrb
-        working-directory: ./drivers/riverqueue-activerecord
+        working-directory: ./driver/riverqueue-activerecord
 
       - name: bundle install (riverqueue-sequel)
         run: bundle install
-        working-directory: ./drivers/riverqueue-sequel
+        working-directory: ./driver/riverqueue-sequel
 
       - name: Standard Ruby (riverqueue-sequel)
         run: bundle exec standardrb
-        working-directory: ./drivers/riverqueue-sequel
+        working-directory: ./driver/riverqueue-sequel
 
   type_check:
     runs-on: ubuntu-latest
@@ -143,16 +143,16 @@ jobs:
 
       - name: bundle install (riverqueue-activerecord)
         run: bundle install
-        working-directory: ./drivers/riverqueue-activerecord
+        working-directory: ./driver/riverqueue-activerecord
 
       - name: Rspec (riverqueue-activerecord)
         run: bundle exec rspec
-        working-directory: ./drivers/riverqueue-activerecord
+        working-directory: ./driver/riverqueue-activerecord
 
       - name: bundle install (riverqueue-sequel)
         run: bundle install
-        working-directory: ./drivers/riverqueue-sequel
+        working-directory: ./driver/riverqueue-sequel
 
       - name: Rspec (riverqueue-sequel)
         run: bundle exec rspec
-        working-directory: ./drivers/riverqueue-sequel
+        working-directory: ./driver/riverqueue-sequel