Add missing activity types for pull_request and pull_request_target (#242)

Fixes #51

Added the following activity types to pull_request and pull_request_target:
- milestoned
- demilestoned
- enqueued
- dequeued

These types were missing from workflow-v1.0.json but are valid workflow
triggers per GitHub docs.

Also added schema-sync.test.ts to ensure activity types in workflow-v1.0.json
stay in sync with webhooks.json. The test:
- Checks both directions (webhooks→schema and schema→webhooks)
- Has WEBHOOK_ONLY for types not valid as workflow triggers:
  - check_suite: requested, rerequested
  - registry_package: default
- Has SCHEMA_ONLY for types valid in workflows but not in webhooks:
  - registry_package: updated
- Has NAME_MAPPINGS for naming differences:
  - project_column: edited (webhook) ↔ updated (schema)
- Provides actionable error messages when mismatches are found

workflow-parser/testdata/reader/events-mapping-all.yml

@@ -120,6 +120,8 @@ on:
       - unassigned
       - labeled
       - unlabeled
+      - milestoned
+      - demilestoned
       - opened
       - edited
       - closed
@@ -129,6 +131,8 @@ on:
       - ready_for_review
       - locked
       - unlocked
+      - enqueued
+      - dequeued
       - review_requested
       - review_request_removed
       - auto_merge_enabled
@@ -160,6 +164,8 @@ on:
       - unassigned
       - labeled
       - unlabeled
+      - milestoned
+      - demilestoned
       - opened
       - edited
       - closed
@@ -169,6 +175,8 @@ on:
       - ready_for_review
       - locked
       - unlocked
+      - enqueued
+      - dequeued
       - review_requested
       - review_request_removed
       - auto_merge_enabled
@@ -386,6 +394,8 @@ jobs:
         "unassigned",
         "labeled",
         "unlabeled",
+        "milestoned",
+        "demilestoned",
         "opened",
         "edited",
         "closed",
@@ -395,6 +405,8 @@ jobs:
         "ready_for_review",
         "locked",
         "unlocked",
+        "enqueued",
+        "dequeued",
         "review_requested",
         "review_request_removed",
         "auto_merge_enabled",
@@ -441,6 +453,8 @@ jobs:
         "unassigned",
         "labeled",
         "unlabeled",
+        "milestoned",
+        "demilestoned",
         "opened",
         "edited",
         "closed",
@@ -450,6 +464,8 @@ jobs:
         "ready_for_review",
         "locked",
         "unlocked",
+        "enqueued",
+        "dequeued",
         "review_requested",
         "review_request_removed",
         "auto_merge_enabled",