fix(types): fix core types to better handle middleware types

[dai-shi]

close #638
It generally improves the compatibility for pre v3.6.

[github-actions]

Size Change: -1 B (0%)

Total Size: 11.2 kB

Filename	Size	Change
dist/index.js	1.35 kB	-1 B (0%)

ℹ️ View Unchanged

Filename	Size
dist/context.js	622 B
dist/esm/context.js	521 B
dist/esm/index.js	1.23 kB
dist/esm/middleware.js	2.77 kB
dist/esm/shallow.js	272 B
dist/esm/vanilla.js	520 B
dist/middleware.js	2.93 kB
dist/shallow.js	318 B
dist/vanilla.js	630 B

_{compressed-size-action}

[codesandbox-ci]

This pull request is automatically built and testable in CodeSandbox.

To see build info of the built libraries, click here or the icon next to each commit SHA.

Latest deployment of this branch, based on commit 893712e:

Sandbox	Source
React	Configuration
React Typescript	Configuration
React Browserify	Configuration
React Snowpack	Configuration
React Parcel	Configuration
Next.js	Configuration
TypeScript (forked)	Issue #638

[dai-shi]

https://codesandbox.io/s/typescript-forked-mgpys
@andreechristian this fixes it!