adding file for sql 50 problem 1211

adding solution to SQL 50 1633

adding problem links to 1075 and 1251

adding solution to SQL 50 number 1075

adding solution to SQL 50 1251

adding solution to sql 50 question 620

adding 620 file

Enhance notes for confirmation rate calculation

Add SQL query for calculating confirmation rate

updating readme to include sql 50 example

Update README.md

adding problem 1934 file

adding solution to problem 570

Create 2130-Maximum-Twin-Sum-of-a-Linked-List.md

Create 2095-Delete-the-Middle-Node-of-a-Linked-List.md