add opencollective metadata and index field

tests/metadata/dump/com.politedroid.yaml

@@ -23,6 +23,7 @@ Litecoin: null
 MaintainerNotes: ''
 Name: null
 NoSourceSince: '1.5'
+OpenCollective: null
 Provides: null
 Repo: https://github.com/miguelvps/PoliteDroid.git
 RepoType: git

tests/metadata/dump/org.adaway.yaml

@@ -46,6 +46,7 @@ Litecoin: null
 MaintainerNotes: ''
 Name: null
 NoSourceSince: ''
+OpenCollective: null
 Provides: org.sufficientlysecure.adaway
 Repo: https://github.com/dschuermann/ad-away.git
 RepoType: git

tests/metadata/dump/org.smssecure.smssecure.yaml

@@ -43,6 +43,7 @@ Litecoin: null
 MaintainerNotes: ''
 Name: null
 NoSourceSince: ''
+OpenCollective: null
 Provides: null
 Repo: https://github.com/SMSSecure/SMSSecure
 RepoType: git

tests/metadata/dump/org.videolan.vlc.yaml

@@ -45,6 +45,7 @@ MaintainerNotes: 'Instructions and dependencies here: http://wiki.videolan.org/A
   '
 Name: null
 NoSourceSince: ''
+OpenCollective: null
 Provides: null
 Repo: git://git.videolan.org/vlc-ports/android.git
 RepoType: git

tests/metadata/info.guardianproject.urzip.yml

@@ -1,6 +1,8 @@
 AutoName: Urzip：本地应用的信息
 AutoUpdateMode: None
 Bitcoin: 1Fi5xUHiAPRKxHvyUGVFGt9extBe8Srdbk
+LiberapayID: '9999999'
+OpenCollective: f-droid-just-testing
 Categories:
 - Development
 - GuardianProject