feat: add gitea/forgejo support

src/providers/index.ts

@@ -0,0 +1,22 @@
+import type { Provider } from "./types";
+import { githubProvider } from "./github";
+import { giteaProvider } from "./gitea";
+
+export type { Provider } from "./types";
+export { verifySignature } from "./github/verify";
+
+/**
+ * Detection order matters: Gitea webhooks also send GitHub-compatible headers
+ * (`X-GitHub-Event`, `X-Hub-Signature-256`, ...), so a Gitea request would
+ * match the GitHub provider too. Check Gitea first — real GitHub requests
+ * never send `X-Gitea-Event`.
+ */
+const providers: Provider[] = [giteaProvider, githubProvider];
+
+/**
+ * Pick the webhook provider for a request based on its headers (e.g.
+ * `X-GitHub-Event` / `X-Gitea-Event`). Returns null when no provider matches.
+ */
+export function detectProvider(headers: Record<string, string>): Provider | null {
+  return providers.find((p) => p.matches(headers)) ?? null;
+}