An mssql Persister for SQL Server and Azure SQL?

[nltgpeterskoglund]

Would you be open to a persister-mssql module? It would bind to the mssql
package, which covers SQL Server, Azure SQL Database and Azure SQL Managed
Instance in one go, and would follow the persister-pg shape: you pass in a
ConnectionPool you configured yourself, so TinyBase stays out of the Azure
authentication story.

Scope I have in mind for a first PR:

• JSON serialization only, for both Store and MergeableStore. Tabular
  needs per-table change detection, which is the expensive part on SQL Server,
  so I would leave it for later.
• Auto-loading polls a rowversion column rather than using notifications.
  Service Broker is not available on Azure SQL Database and Change Tracking
  needs ALTER DATABASE, so neither seemed right to require.
• mssql as an optional peer dependency, and a variant in the database matrix.

One thing worth flagging before I open anything: T-SQL needs three small
dialect parameters threaded through the shared database code — WHERE(true)
is not valid, nvarchar(max) cannot be a primary key, and dropping a column
is spelled DROP COLUMN. They default to the current spelling so SQLite and
PostgreSQL emit byte-identical SQL, but it does touch files every Persister
shares. Happy to shape that however you prefer.

I have it working and tested against SQL Server 2022 if that is of interest.

The branch is at
https://github.com/nltgpeterskoglund/tinybase/tree/mssql-persister — four
commits, following the dependency / boilerplate / tests / docs order. Happy to
open it as a PR, or to rework the scope first if you would rather it landed
differently.

[nltgpeterskoglund]

I have opened this as #295 in the meantime, so there is a concrete diff to look at rather than just a description. The scope question above still stands though - happy to close it and rework things here if you would rather it landed differently.