Fixed compatibility issue with Obsidian Tasks plugin (#4).

Preparation for submission to Obsidian plugins repository; notable changes according to guidelines:

• renamed plugin ID to remove obsidian;
• renamed command.

• Auto-update on every change is not possible anymore with modern versions of Obsidian; the plugin now efficiently auto-updates when a checkbox is toggled in a Live Preview editor.
• Added ability to track unchecked checkboxes instead of checked ones; just add a minus before the number or fraction or percent sign: (-/), (-%).
• Now recognizes checkboxes with a - as mark and counts it as checked.