Added secrets to actions to run test example

[JonathanHuot]

No description provided.

[coveralls]

coverage: 90.097%. remained the same
when pulling 59f3d6a on docs-examples
into 7af9125 on master.

[JonathanHuot]

I need to add documentation on "how to add new example", and this will be considered complete. Note that examples are "skipped" if the secrets does not exists (see https://github.com/requests/requests-oauthlib/blob/master/tests/examples/test_native_spa_pkce_auth0.py#L13) .
In this MR, we have all tests passed, so the "optional" tests are not skipped.

[jtroussard]

Will the docs contain guidance on how to load/maintain the secrets?

[JonathanHuot]

Hi @jtroussard & al, you can check docs locally but I think it is good for a first revision.
Any comments are welcome.

[jtroussard]

@JonathanHuot sorry to revive this one. First off, amazing contribution. Second, my apologies, I must have missed this notification and did not see this PR or request to review. I was only alerted to this once the merged notification hit my dashboard.

After reviewing your native spa example, and the new documentation, I've set out to update some of our other examples. I might have some clarifying questions coming soon. Thanks for this again!