dd v5_baseline metrics to comparison table

ver: v5_baseline | Loss: 2.0449 | PPL: 7.73 | BPC: 2.95 (Trained with Unsloth)

dd v4_pure_KR metrics to comparison table

ver: v4_pure_KR | Loss: 2.0590 | PPL: 7.84 | BPC: 2.97 (Trained with Unsloth)

Update README with metrics for v2_baseline

ver: v2_baseline | Loss: 2.0091 | PPL: 7.46 | BPC: 2.90 (Trained with Unsloth)

v1_baseline - Eval Loss: 2.0516, PPL: 7.78 (Trained with Unsloth)

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initial commit