Pre-built custom sql.js for sqliteviz (#62)

* Proof-of-concept pre-built custom sql.js

* Rewrite Makefile as a couple of comprehensible Python scripts

* Add link to a blog post about transitive closure in SQLite

* Remove eval extension -- no much point as it only returns a string

* Consistently use existing Path objects

* Add basic tests scalar functions from extension-functions.c

* Test presence of functions from the rest of built extensions

* Use the same sqlite.com domain

* Add a couple SQLite compile flags that may make it a bit faster

* Add regexpi function test

* Add node about regexpi and REGEXP operator

* Workaround first build failure, rebuild lock file and minor fixes

lib/sql-js/package.json

@@ -0,0 +1,4 @@
+{
+  "name": "sql.js",
+  "main": "./dist/sql-wasm.js"
+}