Option to set topup percentage/limit

**Is your feature request related to a problem? Please describe.**
Most of the time, the battery charge limit is set to 50%. When needed, I click on the **Top Up** button so it charges to 100% by the time I need to go out. But still, I use the app bc I'd like to preserve battery life, and I figure topping up to 100% every time isn't helping. The MacBook's battery-life is pretty good too, so I only need 70-80% per outing.

**Describe the solution you'd like**
I'd like a setting inside the **Charge** or **Feature** menu to set a **Top Up** limit %. By default it'd be 100%, but we can change it to whatever we want, as long as it's higher than the current **Limit** %. That way, we can still use the **Top Up** button.

**Describe alternatives you've considered**
I can just change the **Limit** to 90% each time, but then I'd need to change it back to 50% after that, every time. That's a bother, and it's a waste of the **Top Up** button.