Nested ordered list resumes child's numbering

[ghost]

Describe the bug After nesting an ordered list and returning to the first level, the index resumes the child's numbering. This also happens when you nest a list inside another nested list.

To Reproduce

1. Compose a new email, reply to an existing one or edit a draft.
2. Select Ordered List
3. Write something at index 1.
4. Nest a list inside it (insert a new line and tabulate)
5. Add a few lines
6. Go back to the first level (shift+tab)

When nesting lists inside nested lists, the same thing happens.

Expected behaviour You would expect something like this:

1. Section A

   1. Subsection A
   2. Subsection B

2. Section B

3. Section A

   1. Subsection A
   2. Subsection B
      1. Subsubsection A
      2. Subsubsection B
      3. Subsubsection C
   3. Subsection C

4. Section B

Screenshots (this is on mail.protonmail.ch) (this is on beta.protonmail.ch)

Desktop (please complete the following information):

• OS: Ubuntu 20.04
• Browser Firefox
• Version 76.0.1
• Plugins uBlock Origin and LanguageTool
• Resolution 1920x1080
• URL mail.protonmail.com and dev.protonmail.com

[ghost]

Closing as this is a Firefox specific issue.