Support Saxon's SQL extension functions

[jperterm]

I would appreciate if the VSC extension supports Saxon's SQL extension functions for the following benefits:

• Prevent errors like

  XPath: Function: 'sql:prepared-query' with 2 arguments not found

• Code completion

• Check names/signatures

• Give signature hints

Namespace: http://saxon.sf.net/sql

Functions:

• connect#1
• delete#3
• execute#2
• insert#3
• prepared-query#2
• prepared-statement#2
• query#3
• query#4
• update#4

See also: https://www.saxonica.com/documentation11/index.html#!functions/sql

Let me know, if I can do/prepare something for this to work. Looking at the code it seems that this could be added without much effort even by myself.

[pgfearo]

I will schedule this SQL function support to be added in the next release.

[pgfearo]

I've updated the data for code completion and checking of names/signatures for the SQL functions, ready for release. The SQL function signature help will be provided in a later release once I've implemented a helpProvider for all functions, but this might not be for a while.

[jperterm]

Thanks so much, Phil!