Allow building of sqlite JSON1 extension when building internal sqlite library

[richardhozak]

I added cmake option to enable json1 extension when building internal sqlite library.
I added the option under the SQLITECPP_INTERNAL_SQLITE if statement so it is clear that this option is only valid when building the internal sqlite library.

[coveralls]

Coverage remained the same at 100.0% when pulling 0d2294e on zxey:feature-json1-extension into 9106e8d on SRombauts:master.

[SRombauts]

Hi @Zxey I wasn't aware of this extension, do you know since when it exists?

Anyway, I think it's a great feature 👍

The only small change I would propose is to actually set SQLITE_ENABLE_JSON1 publicly so the client code would be able to test for this feature.

[richardhozak]

It seems that it has been available since sqlite version 3.9.0 as seen in changelog https://sqlite.org/search?s=c&q=JSON1

[SRombauts]

See PR #428 for the new branch I just pushed:
I am going to remove option SQLITE_ENABLE_JSON1 since the JSON functions and operators are built into SQLite by default, as of SQLite version 3.38.0 (2022-02-22).

For us with SQLiteCpp it would be since Version 3.2.0 - 2022 September 18