Doc about `fedify webfinger` command in `CHANGE.md`

     -  Added `MemoryKvStore.cas()` method.

     -  Added `DenoKvStore.cas()` method.

 -  Added `fedify webfinger` command. This command allows users to look up

    WebFinger information for a given resource.

    -  The input can be a handle (e.g., `@user@server`, `user@server`) or

       a URL (e.g., `https://server/users/path`).

    -  The `--user-agent` or `-a` option used as `User-Agent` header value

       in the WebFinger request.

    -  The `--allow-private-address` or `-p` option allows looking up

       WebFinger information for private addresses (e.g., `localhost`).

Version 1.7.2

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