[Javadoc]: Add usage examples to CharSet.contains Javadoc (#1605)

* [Javadoc]: Add usage examples to `CharSet.contains` Javadoc

* [Javadoc]: Fix minor punctuation in `CharSet.contains` Javadoc

* [Javadoc]: Standardize parameter description in `CharSet.contains` Javadoc - revert to original form

* [Javadoc]: Expand and copy examples in `CharSet.contains` Javadoc for clarification from class level.

* Clarify examples for negation character in CharSet

Updated example description to clarify usage of negation character.

---------

Co-authored-by: Gary Gregory <garydgregory@users.noreply.github.com>

Author: Milanx22

src/main/java/org/apache/commons/lang3/CharSet.java

@@ -221,6 +221,17 @@ protected void add(final String str) {
      * Does the {@link CharSet} contain the specified
      * character {@code ch}.
      *
+     * <p>Examples using the negation character:</p>
+     * <pre>
+     *     CharSet.getInstance("^a-c").contains('a') = false
+     *     CharSet.getInstance("^a-c").contains('d') = true
+     *     CharSet.getInstance("^^a-c").contains('a') = true // (only '^' is negated)
+     *     CharSet.getInstance("^^a-c").contains('^') = false
+     *     CharSet.getInstance("^a-cd-f").contains('d') = true
+     *     CharSet.getInstance("a-c^").contains('^') = true
+     *     CharSet.getInstance("^", "a-c").contains('^') = true
+     * </pre>
+     *
      * @param ch  the character to check for
      * @return {@code true} if the set contains the characters
      */