Feature request: persistent weak-letter tracking with a separate "practice weak letters" test

[ripasso]

I keep making mistakes on the same letters, but there's no good way to drill them other than 'practice words' that only persists throughout one test. I noticed that there is a 'weakspot' funbox also which gets refreshed after a reload, and it changes the words in your normal tests.

I am suggesting a passive tracker that:

1. notes down for each letter:

• how many times it was typed;
• how many of those were mistakes;
• the average time taken;
• which letter was typed instead (e.g. r → t).

2. doesn't change the words in your normal tests like 'weakspot' does, and it gets synced to the account so it can persist if the user likes (there should be an option to turn it off if someone doesn't wish it to be tracked).

3. has a keyboard heat map similar to keybr.com where you can see the success rate of each letter, and also pick a time range that you would like to practice your wrong letters/words from: the past day, week or month.

4. counts towards your stats similar to 'practice words' which appears after every test as a custom test type.