Feature Idea: Spell Checking Mode (to control timing)

**What problem does this solve?**
Currently the spell checking is run in real time. This is functionally fine, but appears a bit visually distracting when looking at the typed text. Typically for me, incorrectly spelled words are worth correcting _after_ finishing typing the current sentence, so I feel this would allow a more natural flow.

**Proposed Solution**
An option in settings to configure the timing for when spell checking is applied. This would allow the user to choose when they'd like it to happen.

**Example**
Concept for a new settings option:

 
As an idea, this would allow a few options. Firstly the current default behaviour can be maintained.

Then alternatively, only check spelling after the spacebar is pressed. Then it would show any incorrectly spelled words after each is fully typed. Maybe even this could be expanded to include end of sentence punctuation.

Or another option would be only check spelling after typing stops (e.g. after 1-2 seconds without a keystroke).

 
**Component**
- [ ] Core engine
- [x] Plugin/Extension
- [ ] Other: _____

 
**Additional Context**
I feel this would be a very handy option. Crucially to maintain the current default for those who prefer the status quo, and then new options for fine-tuning when spell checking is applied.

Thank you for your continued work on this excellent addon!

The issue names no files, tests, or entry points; start by locating the plugin settings and the current spell-check trigger. Define how each timing option behaves while preserving the current default, then verify that checking occurs after the selected event or idle interval.

Written by the indexing model from the issue text.