added load_clean.R and added data to .gitignore

[Ddfulton]

Dear Jeff,

This data is incredible but it's not quite plug and play yet. I made an R Script that gets it there and saves it in an .rds file (R-readable compressed format). This could easily be saved as a .csv, Parquet or .h5 for the Python users out there too. What I did was

1. Load all the points .csv's and combine them into one dataframe
2. Fix the last name problem (for example making "A. de. Minaur" and "Alex de Minaur" both into "a minaur".
3. Infer the event_name
4. Make a column for the surface

Please consider merging my PR as it'll make the time-to-first-plot substantially lower for any future users.

[ALEX98320]

Dear data author
I would like to ask two questions. Firstly, what is the definition of P1Momentum in the data? Secondly, in 2020 Wimbledon, the 22nd French Open, the 22nd Australian Open, the 23rd US Open, the 23rd French Open, and the 23rd Australian Open, I have found some omissions. May I ask if there are any additions. Can I help you supplement how to obtain these missing data at the same time. Hope to cooperate with you. Please reply: [email protected]