update website links to OpenCollective

Author: epoberezkin

docs/README.md

@@ -39,24 +39,24 @@ Use JSON Type Definition or JSON Schema
 ## Ajv sponsors
 
 [![mozilla](/img/mozilla.svg)](https://www.mozilla.org)
-[![reserved](/img/reserved.svg)](https://github.com/sponsors/epoberezkin)
+[![reserved](/img/reserved.svg)](https://opencollective.com/ajv)
 
 </Sponsors>
 
 <Sponsors level="gold">
 
 [![microsoft](/img/microsoft.png)](https://opensource.microsoft.com)
-[![reserved](/img/reserved.svg)](https://github.com/sponsors/epoberezkin)
-[![reserved](/img/reserved.svg)](https://github.com/sponsors/epoberezkin)
+[![reserved](/img/reserved.svg)](https://opencollective.com/ajv)
+[![reserved](/img/reserved.svg)](https://opencollective.com/ajv)
 
 </Sponsors>
 
 <Sponsors level="bronze">
 
 [![retool](/img/retool.svg)](https://retool.com/?utm_source=sponsor&utm_campaign=ajv)
 [![tidelift](/img/tidelift.svg)](https://tidelift.com/subscription/pkg/npm-ajv?utm_source=npm-ajv&utm_medium=referral&utm_campaign=enterprise)
-[![reserved](/img/reserved.svg)](https://github.com/sponsors/epoberezkin)
-[![reserved](/img/reserved.svg)](https://github.com/sponsors/epoberezkin)
+[![reserved](/img/reserved.svg)](https://opencollective.com/ajv)
+[![reserved](/img/reserved.svg)](https://opencollective.com/ajv)
 
 </Sponsors>