feat: Detect videoplayback proxy from invidious-companion and add it to the CSP header

src/invidious/helpers/backend_info.cr

@@ -0,0 +1,17 @@
+module BackendInfo
+  extend self
+  @@exvpp_url : String = ""
+
+  def get_videoplayback_proxy
+    begin
+      response = HTTP::Client.get "#{CONFIG.invidious_companion.sample.private_url}/info"
+      exvpp_url = JSON.parse(response.body)["external_videoplayback_proxy"].to_s
+      @@exvpp_url = exvpp_url
+    rescue
+    end
+  end
+
+  def get_exvpp
+    return @@exvpp_url
+  end
+end