Add Open Collective

https://opencollective.com/ruby-oauth

Author: pboling

.github/FUNDING.yml

@@ -6,8 +6,8 @@ github: [pboling] # Replace with up to 4 GitHub Sponsors-enabled usernames e.g.,
 issuehunt: pboling # Replace with a single IssueHunt username
 ko_fi: pboling # Replace with a single Ko-fi username
 liberapay: pboling # Replace with a single Liberapay username
-open_collective: # Replace with a single Open Collective username
+open_collective: ruby-oauth # Replace with a single Open Collective username
 patreon: galtzo # Replace with a single Patreon username
 polar: pboling
 thanks_dev: u/gh/pboling
-tidelift: rubygems/oauth-tty # Replace with a single Tidelift platform-name/package-name e.g., npm/babel
+tidelift: rubygems/oauth-tty # Replace with a single Tidelift platform-name/package-name e.g., npm/babel