Fix depguard config in yml

[pohang]

This PR fixes the following issues:

• packages-with-error-messages should be packages-with-error-message based on the mapstructure tag from https://github.com/golangci/golangci-lint/blob/master/pkg/config/config.go#L165

• Due to Period in map key name breaks when unmarshalling to struct spf13/viper#348, after fixing above typo, it'll fail with

* 'linters-settings.Depguard.packages-with-error-message[github]' expected type 'string', got unconvertible type 'map[string]interface {}'

since alot of package names will have dots in them. A workaround is to specify as a list of maps, which will get merged by mapstructure (see config). Viper does have WeaklyTypedInput enabled by default.

[claassistantio]

All committers have signed the CLA.

[tpounds]

@pohang Thanks for the contribution! Can you make your updates to README.tmpl.md and rerun with make README.md and then add both files to the pr?

[pohang]

@tpounds All the changes to README.tmpl.md come from updating the two .yml files and then running make README.md. I don't think that updating README.tmpl.md is necessary here.

[tpounds]

🚀 it!

[tpounds]

@pohang My mistake. It looks like the tests were failing for an unrelated issue. I've merged in your commit. Thanks!