Implement functions to convert between infix, postfix and prefix notations

[nbro]

TODO

• Implement infix-to-postfix
• Implement infix-to-prefix
• Implement postfix-to-infix
• Implement prefix-to-postfix
• Write tests

Resources

• https://en.wikipedia.org/wiki/Polish_notation
• https://en.wikipedia.org/wiki/Reverse_Polish_notation