feat: wrap-aware line heights

[StevenEWright]

This change leverages the new line metrics in the last PR to make highlights and the gutter respect wrapped line in the editor properly.

It also introduces a more powerful highlighting API.

Calling .createHighlight() on the editor now produces a reactive highlight object:

export interface Highlight {
  /** The line number to highlight. */
  get lineNumber(): number;
  set lineNumber(lineNumber: number);

  /** Whether or not the highlight is visible. */
  get visible(): boolean;
  set visible(visible: boolean);

  /** The CSS class to apply to the highlight. */
  get cssClass(): string;
  set cssClass(cssClass: string);

  /** Deletes the highlight. */
  delete(): void;
}

Shown all together:

**Github Issue List: ** closes #18

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[github-actions]

size-limit report 📦

Path	Size
./dist/kullna-editor.min.js	7.03 KB (+4.91% 🔺)