Update some Algorithms, Stats courses (#411)

* Add 6.5210 / 6.854 / 18.415 (FA13/20/21/22)

* Add UCLA Stats 21 (SP21)

README.md

@@ -174,7 +174,7 @@ Table of Contents
 - [Harvard Information Theory 2022, by Gregory Falkovich](https://www.youtube.com/playlist?list=PLDEN2FPNHwVZKAFqfFl1b_NNAESTJwV9o)
 - [Math 510 - Linear Programming and Network Flows - Colorado State University](https://www.math.colostate.edu/~adams/teaching/math510fall2020/)
 - [LINFO 2266 Advanced Algorithms for Optimization 2021, by Pierre Schaus - UCLouvain](https://www.youtube.com/playlist?list=PL682UO4IMem-wgYnJl5yMswlNkve_8oGU)
-- [MIT 6.854 / 18.415 Advanced Algorithms spring 2016, by Ankur Moitra](https://www.youtube.com/playlist?list=PL6ogFv-ieghdoGKGg2Bik3Gl1glBTEu8c)
+- [MIT 6.5210 / 6.854 / 18.415 Advanced Algorithms Fall 2013, 2020, 2021, 2022, by David Karger](https://6.5210.csail.mit.edu/materials) ([Spring 2016, by Ankur Moitra](https://www.youtube.com/playlist?list=PL6ogFv-ieghdoGKGg2Bik3Gl1glBTEu8c))
 - [CMU 10 801 Advanced Optimization and Randomized Algorithms spring 2014, by Suvrit Sra and Alex Smola](https://www.cs.cmu.edu/~suvrit/teach/)
 - [UC Santa Cruz CSE 101 Intro to Data Structures and Algorithms fall 2022, by Seshadhri Comandur](https://www.youtube.com/playlist?list=PLOQjlWvnI0fY1BCDxdiUSwkRHjnNI73G6) ([Fall 2020](https://www.youtube.com/playlist?list=PLOQjlWvnI0fZGffr1_MqCoaC5nUVtQIWz))
 - [UC Santa Cruz CSE 201 Analysis of Algorithms winter 2022, by Seshadhri Comandur](https://www.youtube.com/playlist?list=PLOQjlWvnI0fYmOmrAAN-g1d4nFB2uz6tU)
@@ -459,7 +459,7 @@ Table of Contents
   - [LMU Munich Introduction to Machine Learning](https://slds-lmu.github.io/i2ml/)
   - [CMU 15 388 / 15 688 Practical Data Science, by Zico Kolter](https://www.datasciencecourse.org/lectures/) ([Fall 2019](https://scs.hosted.panopto.com/Panopto/Pages/Sessions/List.aspx#folderID=%22618ea253-ca45-4b14-9f1d-aab501543bd2%22)) ([Spring 2018](https://scs.hosted.panopto.com/Panopto/Pages/Sessions/List.aspx#folderID=%22912b80a3-625d-405d-8905-a8620133666b%22))
   - [UCLA Stats 15 Introduction to Data Science fall 2022, by Miles Chen](https://www.youtube.com/playlist?list=PLIygTcviGPKCEzYDpJha6hP6ne-50sT1o)
-  - [UCLA Stats 21 Python and Other Technologies for Data Science spring 2024, by Miles Chen](https://www.youtube.com/playlist?list=PLIygTcviGPKAdsiprcbdk5HHPxS6PloWE)
+  - [UCLA Stats 21 Python and Other Technologies for Data Science spring 2024, by Miles Chen](https://www.youtube.com/playlist?list=PLIygTcviGPKAdsiprcbdk5HHPxS6PloWE) ([Spring 2021](https://www.youtube.com/playlist?list=PLKR7271tMEmgBPgu4LtjDhX3ywpTxda5g))
   - [UCLA Stats C161/C261 Introduction to Pattern Recognition and Machine Learning winter 2024, by Arash Amini](https://www.youtube.com/playlist?list=PLN_qg0-2-0SxQ2vlXxlZVMKkt4gI1YYP8) ([Winter 2023](https://www.youtube.com/playlist?list=PLN_qg0-2-0SwLCXGUyM3FNSRwG6GNgONr))
   - [UCLA Stats 231C Theories of Machine Learning spring 2022, by Arash Amini](https://www.youtube.com/playlist?list=PLN_qg0-2-0SxKyZLv_FotPDED5ET_rQmo)
   - [MSU Machine Learning](https://www.youtube.com/watch?v=kMf0qDtQ_PM&list=PLZ-krWGO-UEyPHsZfOjYH03_TyIN2pPhl&pp=iAQB)