stitching: cite DpSeamFinder reference

doc/opencv.bib

@@ -27,6 +27,18 @@
   publisher = {IEEE Computer Society},
   address = {Washington, DC, USA},
 }
+@article{MillsD09,
+  author = {Mills, Alec and Dudek, Gregory},
+  title = {Image stitching with dynamic elements},
+  journal = {Image and Vision Computing},
+  year = {2009},
+  volume = {27},
+  number = {10},
+  pages = {1593--1602},
+  publisher = {Elsevier},
+  doi = {10.1016/j.imavis.2009.03.004},
+  url = {https://doi.org/10.1016/j.imavis.2009.03.004}
+}
 @article{Zhao23,
   author = {Zhao, Xiaoming and Wu, Xingming and Chen, Weihai and Chen, Peter C. Y. and Xu, Qingsong and Li, Zhengguo},
   title = {ALIKED: A Lighter Keypoint and Descriptor Extraction Network via Deformable Transformation},

modules/stitching/include/opencv2/stitching/detail/seam_finders.hpp

@@ -117,6 +117,8 @@ private:
 };
 
 
+/** @brief Dynamic programming-based seam estimator. See @cite MillsD09 for a related approach.
+ */
 class CV_EXPORTS_W DpSeamFinder : public SeamFinder
 {
 public: