feat: adding support for before middleware

[ibash]

This adds a beforeMiddleware option to the config. This allows the user to inject middleware before karma's middleware are ran. My use case is blocking the tests on refresh while the tests are recompiling (to prevent old test files from being served).

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[ibash]

I signed it!

[googlebot]

CLAs look good, thanks!

[dignifiedquire]

Thanks for the contribution! Could you please add a set of tests that cover this to ensure this is doing what is expected. (e2e as well as unit tests)

[ibash]

@dignifiedquire I added tests similar tot he middleware tests that were existing -- is that sufficient?

[ibash]

@dignifiedquire bump

[ibash]

Rebased on master to resolve conflicts

[ibash]

bump @dignifiedquire

[dignifiedquire]

Thanks