Create data folder if it does not exist

[hamirmahal]

No description provided.

[hamirmahal]

It can be a poor user experience if every time I exit numbat I see an error message about the history failing to save, without any automatic fixes or suggestions.

[hamirmahal]

hamir@Laptop:~/numbat$  cargo run
    Finished dev [unoptimized + debuginfo] target(s) in 0.21s
     Running `target/debug/numbat`

  █▄░█ █░█ █▀▄▀█ █▄▄ ▄▀█ ▀█▀    Numbat 1.10.1
  █░▀█ █▄█ █░▀░█ █▄█ █▀█ ░█░    https://numbat.dev/

>>>  cos (25 deg)

  cos(25 degree)

    = 0.906308 

>>> 
>>> 
Error while saving history to '/home/hamir/.local/share/numbat/history': No such file or directory (os error 2): No such file or directory (os error 2)
hamir@Laptop:~/numbat$  cargo run
    Finished dev [unoptimized + debuginfo] target(s) in 0.20s
     Running `target/debug/numbat`

  █▄░█ █░█ █▀▄▀█ █▄▄ ▄▀█ ▀█▀    Numbat 1.10.1
  █░▀█ █▄█ █░▀░█ █▄█ █▀█ ░█░    https://numbat.dev/

>>>  cos (25 deg)

  cos(25 degree)

    = 0.906308 

>>> 
>>> 
Error while saving history to '/home/hamir/.local/share/numbat/history': No such file or directory (os error 2): No such file or directory (os error 2)

[hamirmahal]