Add funding_uri to gemspec

Author: rmm5t

strip_attributes.gemspec

@@ -4,6 +4,7 @@ $LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
 require "strip_attributes/version"
 
 Gem::Specification.new do |spec|
+  username         = "rmm5t"
   spec.name        = "strip_attributes"
   spec.version     = StripAttributes::VERSION
   spec.authors     = ["Ryan McGeary"]
@@ -18,9 +19,10 @@ Gem::Specification.new do |spec|
   spec.require_paths = ["lib"]
 
   spec.metadata = {
-    "bug_tracker_uri"   => "https://github.com/rmm5t/strip_attributes/issues",
-    "changelog_uri"     => "https://github.com/rmm5t/strip_attributes/blob/master/CHANGELOG.md",
-    "source_code_uri"   => "https://github.com/rmm5t/strip_attributes",
+    "bug_tracker_uri"   => "https://github.com/#{username}/#{spec.name}/issues",
+    "changelog_uri"     => "https://github.com/#{username}/#{spec.name}/blob/master/CHANGELOG.md",
+    "source_code_uri"   => "https://github.com/#{username}/#{spec.name}",
+    "funding_uri"       => "https://github.com/sponsors/#{username}",
   }
 
   spec.add_runtime_dependency "activemodel", ">= 3.0", "< 9.0"