Sqlite-fts4

- Fix for compatibility with big-endian systems - the previous fix did not work correctly, this fix has been tested using a QEMU emulated `s390x` image. [6](https://github.com/simonw/sqlite-fts4/issues/6)

- Fix for compatibility with big-endian systems. [6](https://github.com/simonw/sqlite-fts4/issues/6)

- Fixed bug with Vercel demo. Refs 3

Using these functions in a context where no `match` clause is provided (and hence the matchinfo binary buffer is empty) no longer raises an error, it fails silently instead.

[Demo of these functions without a match clause](https://datasette-sqlite-fts4.datasette.io/24ways-fts4?sql=select%0D%0A++++json_object(%0D%0A++++++++"label"%2C+articles.title%2C+"href"%2C+articles.url%0D%0A++++)+as+article%2C%0D%0A++++articles.author%2C%0D%0A++++rank_score(matchinfo(articles_fts%2C+"pcx"))+as+score%2C%0D%0A++++rank_bm25(matchinfo(articles_fts%2C+"pcnalx"))+as+bm25%2C%0D%0A++++json_object(%0D%0A++++++++"pre"%2C+annotate_matchinfo(matchinfo(articles_fts%2C+"pcxnalyb")%2C+"pcxnalyb")%0D%0A++++)+as+annotated_matchinfo%2C%0D%0A++++matchinfo(articles_fts%2C+"pcxnalyb")+as+matchinfo%2C%0D%0A++++decode_matchinfo(matchinfo(articles_fts%2C+"pcxnalyb"))+as+decoded_matchinfo%0D%0Afrom%0D%0A++++articles_fts+join+articles+on+articles.rowid+%3D+articles_fts.rowid&search=)

- Now depends on [sqlite-fts4 1.0.2](https://github.com/simonw/sqlite-fts4/releases/tag/1.0.2) for compatibility with big-endian systems.