feat: Add JWT token type

[pi-kei]

Fix: #99 (comment)

Add TokenType field to casdoorsdk.Claims.
Add IsRefreshToken func to casdoorsdk.Claims.
This feature will let you find out if you are dealing with refresh token or access token.

[casbin-bot]

@tangyang9464 @imp2002 please review

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[github-actions]

🎉 This PR is included in version 0.36.0 🎉

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[pi-kei]

@hsluoyz I'm sorry but I've not tested this properly. So, it is not working as expected. Now casdoorsdk.Claims.TokenType is always equals to access-token because of how json decoder works.

Here's the quote from docs:

To unmarshal JSON into a struct, Unmarshal matches incoming object keys to the keys used by Marshal (either the struct field name or its tag), preferring an exact match but also accepting a case-insensitive match.

Right now it's treating tokenType and TokenType as the same field. To fix that there must be both of them in struct. I can do a fix PR for that.

[hsluoyz]

@pi-kei I told you to test your code locally before submitting it. Now this PR will be reverted. And I have to see your demo video to show the test case running well (but don't submit it) before merging your PR again