doc: add --issues-exit-code=1

[tMinamiii]

This lsp expected exit-code=1 when found lint errors.
If golanci-lint configuration, for example .golanci.yml, defined issues-exit-code: 0, lsp does not work fine.
I think I should add --issues-exit-code=1 README.md Configurations

golangci-lint-langserver/handler.go

Lines 44 to 47 in bcc1b49

	b, err := cmd.Output()
	if err == nil {
	return diagnostics, nil
	}

[tMinamiii]

thx!