Add a page on the Inspector

[mvaligursky]

Adds a User Manual page on the PlayCanvas Inspector, a debug panel for running PlayCanvas applications, under Scripting › Debugging.

Changes:

• New page user-manual/scripting/debugging/inspector:
  • what the Inspector is and what it helps with, with a screenshot;
  • adding it with npm install @playcanvas/inspector and new Inspector(app) or the EntityInspector script, and its options;
  • the toolbar (pause and step, pick, fly, orbit, pop out) and a table of all twelve tabs;
  • stepping through the draws of a frame with the debug frame, with an animation, and a note that it needs the debug engine;
  • the live debug/entity-inspector example.
• Listed in the Debugging section, with an entry on the Debugging overview page.
• Linked from the tools table of the Optimization overview.
• Japanese translations of the page and of both additions.