Add type assertion to is functions

[thebestnom]

Allow for easier use in typescript of is function

[bigmontz]

Thanks for the contribution.

It doesn't see to have harm in the changes you did, but do you mind to add unit some tests?

It could be something like:

const potentialNode :object = getSomeNode()
if (isNode(potentialNode)) {
   potentialNode.identity
}

Apart of this, it looks really nice.

[thebestnom]

@bigmontz added the "test" 😅
didn't find anywhere to put the other tests (no graph types) is but it shouldn't be any different and I don't think any futther tests will make any different

[bigmontz]

🌵

Thanks for your contribution.

Post here whenever it gets released.

[bigmontz]

Type improvement release in version 4.3.4.

Release notes: https://github.com/neo4j/neo4j-javascript-driver/wiki/4.3-changelog#434

cc: @thebestnom