Add soundex function for compatibility

Why it matters

The soundex function enables phonetic matching of strings, allowing users to find words that sound similar despite differences in spelling. This enhances ClickHouse's text search capabilities and improves compatibility with applications relying on soundex for approximate string matching.

How to use it

Use the soundex function in your SQL queries by passing a string expression as an argument, for example:

SELECT soundex('example')
FROM table_name;

This will return the Soundex code representing the phonetic form of the input string.