[FEATURE]: Allow configuring a minimal line width to show the indicator

[Konnichy]

Description

Fixes #17

Type of change

• New feature/enhancement (non-breaking change which adds functionality)
• This change requires a documentation update

How Has This Been Tested

1. Open a new file
2. Start typing characters
3. Check that the indicator shows from 1 character (this default value matches with the previous version of the extension)
4. Add "LWI.minimalLineWidth": 10 in your setting.json
5. Check that the indicator is not shown as long as the editor's cursor is placed on a line less than 10 columns-wide
6. Type more characters
7. Check that the indicator appears from the moment the line becomes 10 columns-wide
8. Change the value of LWI.minimalLineWidth
9. Check that the threshold changed accordingly

Test Configuration:

• OS: Linux (Ubuntu)
• Version: 25.10

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes