ast-tester should validate individual Node type

[azu]

• Add individual Node type for @textlint/ast-node-types #764
• feat(ast-node-types): Add individual Node type and Add Table/TableRow/TableCell node  #1008

We have introduced individual Node type definitions.
However, current @textlint/ast-tester only support TxtNode/TxtParentNode/TxtTextNode.

We want to get more validation based on individual Node types.

TODO

• Generate validator from TypeScript types using ts-json-schema-generator like create-validator-ts
• Add option for test function
  • Probably, some plugin can not to be passed this spec
  • strict option? (or strcitNodeType: ["Paragraph", ....])
  • require flexibility