chore(docs): fix example encoding issue in READMD.md of logger middle…

[Ci-Jie]

When I copied Logging Request ID example to my host for testing
I found that it has some errors about UTF8 encoding
And error message like below:

# command-line-arguments
./main.go:16:2: invalid character U+200B in identifier
./main.go:16:45: cannot refer to unexported name logger.​Config​
./main.go:18:9: invalid character U+200B in identifier
./main.go:18:80: syntax error: unexpected ​, expecting comma or }

Then I tried to use UTF8 GBK encoding
And got the result like below:

鈥媋pp鈥�.鈥婾se鈥�(鈥媗ogger鈥�.鈥婲ew鈥�(logger.鈥婥onfig鈥媨
	// For more options, see the Config section
  Format鈥�: "${pid} ${locals:requestid} ${status} - ${method} ${path}鈥媆n鈥�"鈥�,
}))

So, I fixed it.

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