feat: enhance dev experience

Now it uses luaunit from luarocks and generally provides better make targets, simplifying development process.

#2)

Previously, filters like `$[?(@.a == 0)]` resulted in errors. It fixes them and adds missing tests for them.
Moreover, nested properties access in expressions was malfunction. Now it works, so such filters are possible now: `$[?(@.a.b.c.d == 0)]`.

Previously, filters like `$.array[?(@.keyOfElement < 30)]` didn't work.
You could only do that via recursive child operator, like this: `$..array[?(@.keyOfElement < 30)]`

When type(op1) == 'boolean', this lead to non-nil op2 being converted as true and nil op2 as false. This commit changes this behavior, since null literal is non-nil object and matched in expressions object.field==null to all true fields - during op2 null to boolean coercion, inverted op1 is returned to never match in equality with original value

fix: change null to bool coercion in match_type

Co-authored-by: Vyacheslav Mayorov <v.majorov@picodata.io>