bubblewrap merge does not seem to work with share_target update

Bubblewarp merge doesn't seem to recognize the addition of a share_target to a website's web manifest if it wasn't there before. I haven't tested what happens when the share_target changes.

**Steps to reproduce the behavior:**
1. Have a bubblewrap project initialised on a website that does not have a `share_target` field in it's web manifest
2. Add a `share_target` to the website's manifest
3. Run bubblewrap merge
4. Run bubblewrap update
5. Run bubblewrap build
6. Inspect the generated AndroidManifest.xml

**Expected behavior**
Has an intent filter matching the webshare's share targets
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**Additional context**
This is using the bubblewrap cli installed via npm