Convert a string to sentence case Input:

A string (or the closest thing to that in your language)

Output:

The same string but converted to sentence case

Rules:


For this challenge, sentence case can be considered "The first letter of each sentence is capitalized. The rest are lowercase." (i.e. proper nouns do not have to be capitalized)
If the input does not include a period, it is treated as one sentence.
The other 2 punctuation marks used to end a sentence in english (? and !) can be considered periods
If a letter immediately follows a punctuation mark the same rules still apply (i.e. the first letter is capitalized and all following letters are lowercased until the next punctuation mark)


Sample test cases:

"hello world." // "Hello world."

"CODEGOLF IS FUN." // "Codegolf is fun."

"no period" // "No period"

"the ball was red. so was the balloon." // "The ball was red. So was the balloon." 

"I love codegolf.stackexchange.com" // "I love codegolf.Stackexchange.Com"

"heLLo! hOW are yOU toDay? hOpEfulLy yOu are okay!" // "Hello! How are you today? Hopefully you are okay!"


This is code-golf, so the shortest code wins!
05AB1E, 3 bytes

l.ª


Try it online!

Nothing like a good old built-in answer! This converts the string to lowercase and then performs sentence case.