Update README - Week 8 complete (90/100)

- Week 8: Test Case Management ✅ Complete
- Grade: 90/100 (A-)
- PR #13 merged Jan 4, 2026
- Progress: 8/11 weeks (73%)
- Average grade: 83.1/100 (up from 82.1)
- Added grade progress bar chart with visual trend

Author: aslavchev

README.md

@@ -46,12 +46,29 @@ By the end of this program, your mentee will be able to:
 | 5 | Test Design (Basic) | ✅ Complete | 87/100 | [#9](../../pull/9) | Dec 2, 2025 |
 | 6 | Test Design (Advanced) | ✅ Complete | 76/100 | [#10](../../pull/10) | Dec 7, 2025 |
 | 7 | Test Planning & Strategy | ✅ Complete | 85/100 | [#12](../../pull/12) | Dec 14, 2025 |
-| 8 | Test Case Management | ⏳ Pending | - | - | - |
+| 8 | Test Case Management | ✅ Complete | 90/100 | [#13](../../pull/13) | Jan 4, 2026 |
 | 9 | Agile Testing | ⏳ Pending | - | - | - |
 | 10 | Defect Management | ⏳ Pending | - | - | - |
 | 11 | Python Basics | ⏳ Pending | - | - | - |
 
-**Progress:** 7/11 weeks complete (64%) | **Average Grade:** 82.1/100
+**Progress:** 8/11 weeks complete (73%) | **Average Grade:** 83.1/100
+
+### 📊 Grade Progress Chart
+
+```
+Week 1  ████████████████████████████████████████████ 85/100
+Week 2  ████████████████████████████████████████     82/100
+Week 3  ████████████████████████████████████████     82/100
+Week 4  ███████████████████████████████████          78/100
+Week 5  ███████████████████████████████████████████  87/100
+Week 6  ██████████████████████████████████           76/100
+Week 7  ████████████████████████████████████████████ 85/100
+Week 8  █████████████████████████████████████████████ 90/100 ⭐
+        └────────────────────────────────────────────────────
+        0    10   20   30   40   50   60   70   80   90  100
+
+Average: 83.1/100 | Highest: 90 (Week 8) | Lowest: 76 (Week 6)
+```
 
 ---