Add support for @apollo/client v4

[MasterOdin]

Closes #82

PR adds support for @apollo/client@^4 in the library.

The biggest change necessary for it was moving from compiling the library for es5 to es2015 as @apollo/client now exposes a proper es2015 class, and so errors under es5. Luckily @apollo/client@3 happily works with either. While this is a breaking change, per https://node.green/, anyone using node 6+ is compatible with it, where node 6 was released 9 years ago and hit end of life 7 years ago. At this point, I think anyone still using such an old version of node is also probably not bothering to update their libraries either.

Secondarily, @apollo/client@4 reworked a number of imports, and so to work around this I added a new types.ts file, which uses conditional types to hopefully provide downstream users useful type information. Given I'm bridging two different versions, this necessitated adding a bunch of @ts-ignore to the file due to missing types on v3 and v4 to get it working for testing. Unfortunately, building the library against @apollo/client@3 will throw a bunch of type errors still:

type errors

node_modules/apollo-link-timeout/lib/types/types.d.ts:2:25 - error TS2702: 'ApolloLink' only refers to a type, but is being used as a namespace here.

2 export type Operation = ApolloLink.Operation extends never ? import('@apollo/client/core').Operation : ApolloLink.Operation;
                          ~~~~~~~~~~

node_modules/apollo-link-timeout/lib/types/types.d.ts:2:104 - error TS2702: 'ApolloLink' only refers to a type, but is being used as a namespace here.

2 export type Operation = ApolloLink.Operation extends never ? import('@apollo/client/core').Operation : ApolloLink.Operation;
                                                                                                         ~~~~~~~~~~

node_modules/apollo-link-timeout/lib/types/types.d.ts:3:24 - error TS2702: 'ApolloLink' only refers to a type, but is being used as a namespace here.

3 export type NextLink = ApolloLink.ForwardFunction extends never ? import('@apollo/client/core').NextLink : ApolloLink.ForwardFunction;
                         ~~~~~~~~~~

node_modules/apollo-link-timeout/lib/types/types.d.ts:3:108 - error TS2702: 'ApolloLink' only refers to a type, but is being used as a namespace here.

3 export type NextLink = ApolloLink.ForwardFunction extends never ? import('@apollo/client/core').NextLink : ApolloLink.ForwardFunction;
                                                                                                             ~~~~~~~~~~

node_modules/apollo-link-timeout/lib/types/types.d.ts:4:36 - error TS2702: 'ApolloLink' only refers to a type, but is being used as a namespace here.

4 export type FetchResult<T = any> = ApolloLink.Result extends never ? import('@apollo/client/core').FetchResult<T> : ApolloLink.Result<T>;
                                     ~~~~~~~~~~

node_modules/apollo-link-timeout/lib/types/types.d.ts:4:117 - error TS2702: 'ApolloLink' only refers to a type, but is being used as a namespace here.

4 export type FetchResult<T = any> = ApolloLink.Result extends never ? import('@apollo/client/core').FetchResult<T> : ApolloLink.Result<T>;
                                                                                                                      ~~~~~~~~~~

These errors can be avoided by ensuring you have set "skipLibCheck": true to your tsconfig.json (which is set by default on a fresh tsc --init run) so I think that's acceptable, and I've added a note about it.

Given this, probably makes sense to have this be another major release. We could also just drop support for @apollo/client@3 on the new major version, and only support @apollo/client@4, and then keep the 5.x line alive minimally for any new backwards compatible bugfixes or features that might exist as per the stats on https://www.npmjs.com/package/@apollo/client?activeTab=versions, @apollo/client@3 is still installed more in the past 7 days.

[MasterOdin]

@apollo/client@4 uses null chainging (added in node 14) and ||= operator (added in node 15), so have to drop those versions from testing for it.

[MasterOdin]

execute in @apollo/client@4 requires passing the client that initiating the execute, so this wrapper acts as a shim around that to support both 3 and 4.

[MasterOdin]

New peer dependency for @apollo/client@4.

[MasterOdin]

Closing this in favor of #86. While having the types.ts file is neat in terms of not relying directly on deprecated types for v4, it ends up with too many weird caveats and @ts-ignore failures for comfort.