Add typescript support for apollo.config.ts

Creating a new config with the proper fields is quite burdensome, since the fields allowed are non-obvious and error messaging could be improved. Adding typescript to the apollo config would provide editor completion and an understanding of the acceptable fields/values.

This issue is a feature request for a technical solution, so there may be a better way to accomplish this task, such as a linter

No files, tests, or entry points are identified in the issue. Start by tracing how apollo.config files are discovered, parsed, and validated, then determine whether TypeScript types or a linter best provides completion and accepted values; done means the supported configuration receives useful editor guidance.

Written by the indexing model from the issue text.