Added basic utilities as described in the description.

[MrBisquit]

Added basic utilities:

• checkExists - Checks whether or not an object has value.
• isStringValid - Checks whether or not a string is valid.
• isNumberValid - Checks whether or not a number is valid.
• isArrayValid - Checks whether or not an array is valid.
• getValueOrDefault - Returns the value if it's valid and if not returns the defaultValue.
• doesObjectHaveKey - Checks whether or not an object has a key in it.
• isStringLengthValid - Checks the length of the string is bigger than the minimum and smaller than the maximum (And is valid) These can help because instead of people typing out if statements they can simply import the utilities file and all of the easy to use utilities are in there. If you would like to see more utilities or any changes please let me know as I will be working on these.