feat: automatically create tasks.json when missing (Task #68)

This commit implements automatic tasks.json file creation when it doesn't exist:

- When tasks.json is missing or invalid, create a new one with { tasks: [] }
- Allows adding tasks immediately after initializing a project without parsing a PRD
- Replaces error with informative feedback about file creation
- Enables smoother workflow for new projects or directories

This change improves user experience by removing the requirement to parse a PRD
before adding the first task to a newly initialized project. Closes #494

.changeset/petite-walls-learn.md

@@ -0,0 +1,5 @@
+---
+'task-master-ai': patch
+---
+
+You can now add tasks to a newly initialized project without having to parse a prd. This will automatically create the missing tasks.json file and create the first task. Lets you vibe if you want to vibe."