Update README.md

| State       | Level | Difference |
| ----------- | ----- | ---------- |
| Charging    |    90 |       null |
| Charging    |    95 |          5 |
| Full        |   100 |          5 | <- Include
| Full        |   100 |          0 | <- Ignore
| Discharging |    90 |        -10 |
| Discharging |    80 |        -10 |