fix: body and font for coverage index file

[github-actions[bot]]

🔗 Code Coverage Report for go-test-app-01/ at a33fcc0b7f06bee2347f05107953cd477a1ce7d9

📔 Total: 70.0%
🎯 Threshold: 66.7%
✅ 70.0% >= 66.7%

Full coverage report

``` cointoss/main.go:10: main 75.0% cointoss/main.go:20: tossCoin 66.7% cointoss/main.go:28: maybe 66.7% total: (statements) 70.0% ```

^{go-beautiful-html-coverage ↗}

[github-actions[bot]]

🔗 Code Coverage Report for go-test-app-02/ at a33fcc0b7f06bee2347f05107953cd477a1ce7d9

📔 Total: 70.0%

Full coverage report

``` cointoss/main.go:10: main 75.0% cointoss/main.go:20: tossCoin 66.7% cointoss/main.go:28: maybe 66.7% total: (statements) 70.0% ```

^{go-beautiful-html-coverage ↗}