Working with bullet points was reworked to fix some glitches

[HoffmannTom]

What does this PR do?

Working with bullet points was sometimes problematic when whitespaces were present.
Copy & Paste also caused some trouble.
This PR modifies the bullet point functions For this to work, the dom and range class were extended by adding some helper functions.

Where should the reviewer start?

• best is to start with dom.js and range.js and check the additional methods.
• bullet.js contains major changes

How should this be manually tested?

• use the editor to create and modify lists (OL / UL)

Any background context you want to provide?

If a

element contains formattings or additional elements (div, span), the splitNode function doesn't work well and creates some additional lines or refuses to split. This needs to be addressed in the future. The splitNode function was not modified by this PR.

What are the relevant tickets?

Screenshot (if for frontend)

Checklist

• Added relevant tests or not required
• Didn't break anything