The "permission" pages needs rework to be more readable

[hsluoyz]

These two pages are in bad quality:

• https://casdoor.org/docs/permission/overview

• https://casdoor.org/docs/permission/permission-configuration

• Give more links, more pictures, more GIFs.

• Provide the page name like "Edit Organization", "Edit Role" when talking

• Describe "View rule" & "Modify rule" in "Account items" table of the "Edit Organization" page to control the permission for user fields:

[casbin-bot]

@leo220yuyaodog @Selflocking