Pocketsearch

* Fixed buggy insert_or_update method resulting in faulty token statistics - (https://github.com/kaykay-dv/pocketsearch/issues/60)
* Added documentation on IndexReader class - added verbose parameter (default=False) to .build method - (https://github.com/kaykay-dv/pocketsearch/issues/61 and https://github.com/kaykay-dv/pocketsearch/issues/59)

**Breaking changes**
* PocketSearch.tokens method only returns the top 25 tokens by default instead of all tokens in the index - (https://github.com/kaykay-dv/pocketsearch/issues/62)

* Added more examples to README

* Added support for having multiple connections to in-memory databases (https://github.com/kaykay-dv/pocketsearch/issues/54 and https://github.com/kaykay-dv/pocketsearch/issues/56)
* Added more stable support when using punctuation characters in queries (https://github.com/kaykay-dv/pocketsearch/issues/55)
* Added custom timestamp and date converters for sqlite date/timestamp data types to address Python 3.12 deprecation warning (https://github.com/kaykay-dv/pocketsearch/issues/52)
* Code clean up

**Breaking changes**
* Versions < 0.21 did not support multiple in-memory databases. The second in-memory database trying to establish a connection (with the first one still holding an active connection) would run into a connection time out.

* Small changes to README - now includes gettings started examples
* Added Python 3.12 to list of supported Python versions

* Added connection pool class and made PocketWriter instances thread-safe (https://github.com/kaykay-dv/pocketsearch/issues/44)
* Added possibility to use "legacy" (tables already defined in a sqlite3 database) tables (https://github.com/kaykay-dv/pocketsearch/issues/42)
* Fixed a bug resulting in SQL errors when using the symbol at certain places (https://github.com/kaykay-dv/pocketsearch/issues/49)
* Added proper handling for empty string queries (https://github.com/kaykay-dv/pocketsearch/issues/43)
* Added possiblity to define own "id" fields (https://github.com/kaykay-dv/pocketsearch/issues/42)
* Fixed a bug in SQL trigger definitions

**Breaking changes**
* PocketWriters are now using transactions. If an exception is raised the transaction is rolled back. (https://github.com/kaykay-dv/pocketsearch/issues/45)
* Building the spell checker dictionary has now to be invoked explicitly (https://github.com/kaykay-dv/pocketsearch/issues/46)
* Table creation (FTS5 tables) are now wrapped in an own transaction (https://github.com/kaykay-dv/pocketsearch/issues/45)

* Added context managers PocketReader and PocketWriter
* Added Spell Checker
* Fixed typos in the documentation
* Error that is thrown if a schema field does not have a data type is thrown earlier during schema creation
* Schema field objects are now (shallow-) copied when a schema instance is created to avoid side-effects when multiple schema instances are in use.
* Made PocketSearch._close a public method