[FEATURE] Clear same type of existing formats in the visual region if exists

consider text:

```markdown
hello **world**
```

currently if I select both words and run `<leader>mb`:

```markdown
**hello **world****
```

better output and correct markdown is just remove the inner bold

```markdown
**hello world**
```

I tested both obsidian and typora, they both do this, but github markdown don't do this lol, but I guess it should be good to add.
