code-climate: add default severity

[sinkcup]

when I output code climate format report, GitLab CI code quality report can show the report, but GitLab MR code quality widget can not.

MR: https://jihulab.com/premium-plan/features/04Verify/code-quality-report/golang/-/merge_requests/1

golangci-lint run --enable-all --out-format code-climate:gl-code-quality-report.json

I try to add those required columns in the docs: https://github.com/codeclimate/platform/blob/master/spec/analyzers/SPEC.md#data-types

add type is useless: https://jihulab.com/premium-plan/features/04Verify/code-quality-report/golang/-/merge_requests/3

golangci-lint run --enable-all --out-format code-climate:report.json
cat report.json | jq '.[] += { type: "issue" }' > gl-code-quality-report.json

add severity is usefull: https://jihulab.com/premium-plan/features/04Verify/code-quality-report/golang/-/merge_requests/4

golangci-lint run --enable-all --out-format code-climate:report.json
cat report.json | jq '.[] += { severity: "critical" }' > gl-code-quality-report.json

so I create this PR to add severity default value.

[boring-cyborg]

Hey, thank you for opening your first Pull Request !

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All committers have signed the CLA.

[ldez]

LGTM