Add 'mirror' to the enabled linters in .golangci.yml

[YoshihitoAso]

This pull request introduces minor improvements to code quality and test clarity, as well as a small update to linting configuration. The main changes include switching to more idiomatic Go functions in tests, improving a regular expression usage, and enabling an additional linter.

Code quality and correctness:

• Updated accounts/abi/bind/bind.go to use regexp.MatchString instead of regexp.Match, simplifying the regular expression call and making the code more idiomatic.

Testing improvements:

• Updated three test functions in cmd/geth/accountcmd_plugin_test.go to use WriteString instead of Write([]byte(...)) when writing test data to temporary files, improving code readability and intent. [1] [2] [3]

Linting configuration:

• Added the mirror linter to the .golangci.yml configuration to enhance static analysis coverage.

[Copilot]

Pull Request Overview

This pull request improves code quality through idiomatic Go practices and enhances linting configuration. The changes focus on using more appropriate standard library functions and adding static analysis coverage.

• Replace regexp.Match with regexp.MatchString for more idiomatic string pattern matching
• Update test code to use WriteString instead of Write([]byte(...)) for better readability
• Enable the mirror linter in golangci configuration for additional static analysis

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
cmd/geth/accountcmd_plugin_test.go	Updates three test functions to use WriteString for writing test data to temporary files
accounts/abi/bind/bind.go	Replaces regexp.Match with regexp.MatchString for string pattern matching
.golangci.yml	Adds mirror linter to the enabled linters list

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