Create a function which takes a sentence and returns its abbreviation. Get all of the words over or equal to n characters in length and return the first letter of each, capitalised and overall returned as a single string.
abbreviate("do it yourself") ➞ "Y"
abbreviate("do it yourself", 2) ➞ "DIY"
// "do" and "it" are included because the second parameter specified that word lengths 2 are allowed.
abbreviate("attention AND deficit OR hyperactivity THE disorder")➞ "ADHD"
// Words below the default 4 characters are not included in the abbreviation.
abbreviate("the acronym of long word lengths", 5) ➞ "AL"
// "acronym" and "lengths" have 5 or more characters.
There may not be an argument given for n so set the default to 4.