public String getSplitRange(String value, Range range) {
        return getSplitRange(value, range.getFirst(), range.getLast());
    }
Find the start offset of split

@param chars The input in which we are seeking
@param split  The split number for which we are looking for the start
@return The offset or -1 if it does not exist
analyzer/src/main/java/nl/basjes/parse/useragent/utils/Splitter.java