default Boolean parseBoolean(String value) {
        if (value == null) {
            return null;
        }
        switch (value) {
            case "?0" : return FALSE;
            case "?1" : return TRUE;
            default   : return null;
        }
    }
Determines if the provided value is a sf-boolean.

@param value The value to be parsed
@return True/False or null if this was NOT a boolean.
analyzer/src/main/java/nl/basjes/parse/useragent/clienthints/parsers/CHParser.java