Add docs

lib/pure/strutils.nim

@@ -1396,6 +1396,20 @@ proc format*(formatstr: string, a: varargs[string, `$`]): string {.noSideEffect,
 {.pop.}
 
 proc removeSuffix*(s: var string, chars: set[char] = Newlines) {.rtl.} =
+  ## Removes the first matching character from the string (in-place) given a
+  ## set of characters. If the set of characters is only equal to `Newlines`
+  ## then it will remove both the newline and return feed.
+  ## .. code-block:: nim
+  ##   var
+  ##     userInput = "Hello World!\r\n"
+  ##     otherInput = "Hello!?!"
+  ##   userInput.removeSuffix
+  ##   userInput == "Hello World!"
+  ##   userInput.removeSuffix({'!', '?'})
+  ##   userInput == "Hello World"
+  ##   otherInput.removeSuffix({'!', '?'})
+  ##   otherInput == "Hello!?"
+
   var last = len(s) - 1
 
   if chars == Newlines:
@@ -1412,9 +1426,22 @@ proc removeSuffix*(s: var string, chars: set[char] = Newlines) {.rtl.} =
   s.setLen(last + 1)
 
 proc removeSuffix*(s: var string, c: char) {.rtl.} =
+  ## Removes a single character (in-place) from a string.
+  ## .. code-block:: nim
+  ##   var
+  ##     table = "users"
+  ##   table.removeSuffix('s')
+  ##   table == "user"
   removeSuffix(s, chars = {c})
 
 proc removeSuffix*(s: var string, suffix: string) {.rtl.} =
+  ## Remove the first matching suffix (in-place) from a string.
+  ## .. code-block:: nim
+  ##   var
+  ##     answers = "yeses"
+  ##   answers.removeSuffix("es")
+  ##   answers == "yes"
+
   var newLen = s.len
 
   if s.endsWith(suffix):