Calculate query complexity

[nickoferrall]

When using nest-graphql-endpoint with GitLab, we ran into a bug where too many queries would be batched together. The batched query would be rejected by GitLab as it exceeded the query complexity limit.

To fix, Matt created a PR (#10), enabling us to pass in dataloader options such as a max batch limit.

Currently, we're passing in a max batch limit of 5 (ParabolInc/parabol#6541), but in an ideal world, nest-graphql-endpoint would calculate the complexity and batch appropriately.

AC

• Implement nestGitLabEndpoint following the GitHub example: https://github.com/ParabolInc/nest-graphql-endpoint/blob/main/src/nestGitHubEndpoint.ts
• Calculate the complexity of a query and set an appropriate max batch size if the query will exceed the 250 score limit