[Editor] Improve curve smoothing for Ink tool (bug 1789443)

- Remove the dependency on fit-curve;
- Improve the way to draw the current line in using a Path2D and
  in clearing only the last part of the curve instead of clearing
  all the canvas;
- Smooth the curve when drawing to avoid to have some changes after
  the drawing ends;
- Make the smoothing a bit less agressive.

.eslintrc

@@ -34,7 +34,7 @@
     // Plugins
     "import/extensions": ["error", "always", { "ignorePackages": true, }],
     "import/no-unresolved": ["error", {
-      "ignore": ["pdfjs", "pdfjs-lib", "pdfjs-web", "pdfjs-fitCurve", "web"]
+      "ignore": ["pdfjs", "pdfjs-lib", "pdfjs-web", "web"]
     }],
     "mozilla/avoid-removeChild": "error",
     "mozilla/use-includes-instead-of-indexOf": "error",