cookie support

[tomberek]

Something like this:

diff --git a/server_auth.go b/server_auth.go
index 3acaf2b..6d5379d 100644
--- a/server_auth.go
+++ b/server_auth.go
@@ -108,6 +108,12 @@ func (opts *ServerAuthOptions) createAuthMiddleware(
                return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
                        v := r.Header.Get(headerNameAuthorizer)

+                       if v == "" {
+                                cookie, err := r.Cookie("token")
+                                if err == nil {
+                                        v = "Bearer " + cookie.Value
+                                }
+                        }
                        if v == "" {
                                responseErr(w, ErrUnauthorized.WithHint("missing auth header"))
                                return