fix: switch from action-validator to yamllint (#20)

Turns out action-validator wouldn't have caught the issue introduced in
#15 since it seems to be more concerned with schemas than with valid
YAML, so the next best solution is to run yamllint in CI.

.projenrc.ts

@@ -87,8 +87,6 @@ project.addPeerDeps(
 );
 project.addDevDeps(
   "change-case",
-  "@action-validator/core",
-  "@action-validator/cli",
   "node-fetch@~2" // @TODO this can be removed once we upgrade to Node 18 and use native fetch
 );
 
@@ -99,11 +97,14 @@ new UpgradeCDKTF(project);
 new UpgradeNode(project);
 
 const validateTask = project.addTask("validate-workflows", {
-  exec: `find ./.github/workflows -type f -name "*.yml" -print0 | xargs -0 -n 1 npx action-validator`,
+  exec: `find ./.github/workflows -type f -name "*.yml" -print0 | xargs -0 yamllint -d relaxed`,
 });
 validateTask.description =
-  "Lint the YAML files generated by Projen to define GitHub Actions and Workflows, checking them against published JSON schemas";
-project.postCompileTask.spawn(validateTask);
+  "Lint the YAML files generated by Projen to define GitHub Actions and Workflows using yamllint (installed in CI)";
+project.buildWorkflow?.addPostBuildSteps({
+  name: "Lint the YAML files generated by Projen to define GitHub Actions workflows",
+  run: "npx projen validate-workflows",
+});
 
 // for local developing (e.g. linking local changes to cdktf)
 project.addGitIgnore(".yalc");

projenrc/upgrade-cdktf.ts

@@ -77,12 +77,10 @@ export class UpgradeCDKTF {
                 "chore!: upgrade to cdktf ${{ steps.latest_version.outputs.value }}",
               body: [
                 "This PR initiates the upgrade of CDKTF from version `${{ steps.current_version.outputs.value }}` to version `${{ steps.latest_version.outputs.value }}`.",
-                "Unfortunately, not everything can be automated, and the following steps need to be completed manually:",
-                " ",
+                "Unfortunately, not everything can be automated, and the following steps need to be completed manually:\n",
                 "- [ ] Update `@cdktf/provider-null` to a version compatible with `cdktf@${{ steps.latest_version.outputs.value }}` [here](https://github.com/cdktf/construct-projen-template/blob/d62067602139725e957e516ef41d94c384af731a/.projenrc.ts#L84). Look up the version [here](https://github.com/cdktf/cdktf-provider-null/releases/).",
                 "- [ ] Run `npx projen`",
-                " ",
-                "Please checkout this PR, complete the above steps, push the changes to this branch, and then mark this PR as ready for review to complete the upgrade. Thanks!",
+                "\nPlease checkout this PR, complete the above steps, push the changes to this branch, and then mark this PR as ready for review to complete the upgrade. Thanks!",
               ].join("\n"),
               labels: "automerge,auto-approve,dependencies",
               token: "${{ secrets.PROJEN_GITHUB_TOKEN }}",