Implement strict mode for JSONObject

[stleary]

Strict mode now works for JSONArray (see #877), but not for JSONObject or for JSONArrays embedded in JSONObjects.
For example, the following code parses without error:

        String str = "{\"a\": [b]}";
        JSONObject jsonObject = new JSONObject(str, new JSONParserConfiguration().withStrictMode(true));

Several additional changes should be included with the PR:

• The indentation in nextString(char, boolean) is incorrect.
• There is a compiler warning in JSONTokener that should be fixed: (fixed in add javadoc for strictmode #886)

Warning:  Javadoc Warnings
Warning:  /home/runner/work/JSON-java/JSON-java/src/main/java/org/json/JSONTokener.java:294: warning: no @param for strictMode
Warning:  public String nextString(char quote, boolean strictMode) throws JSONException {
Warning:  ^
Warning: [WARNING] 1 warning