happo for npm release notes

This changes default behavior. Runs that have stale waitForContent or waitFor values will start failing instead of silently producing screenshots with a ~20s timeout penalty per snap.

If you encounter a failure after upgrading:

• Preferred: update the offending waitForContent / waitFor so it matches what is actually rendered. This is almost always the right fix — it removes both the failure and the wasted wait time.
• Last resort: set failOnWaitForTimeout: false in your Happo config to restore the previous warn-and-screenshot behavior while you investigate.

Changes:

• Add failOnWaitForTimeout config option (default: true) to control timeout behavior for waitForContent and waitForSelector — when enabled, timeouts fail the snap with a clear error instead of warning silently [by @lencioni in #500]