Remember GitHub username on filter report forms

@WoodpeckerBaby commented on [Tue Nov 29 2022](https://github.com/AdguardTeam/AdguardFilters/issues/136136)

### Prerequisites

- [X] I checked the documentation and found no answer;
- [X] I checked to make sure that this issue has not already been filed;
- [X] This is not an ad/bug report.

### Problem description

Having to type GitHub username everytime is a lot of work.

### Proposed solution

Remember that on the form, either store that in the app config or in a cookie.

### Additional information

Please simplify the report form and reduce the number of clicks required. The hcapcha should be replaced with Apple's Private Access Tokens where avaliable.