Add indian holidays in calendar hindu.py

[yashwanth2307]

add pongal and ugadhi holidays in calender also there will be holiday for ganesh immersion it can be also added

[PPsyrius]

@yashwanth2307 You might want to include sources or references for the listed holidays above.

If any of them aren’t based on the Gregorian calendar, it’d also be helpful to mention how they’re calculated, along with historical observance records for easier cross-checking. 👍