Add label for links

README.md

@@ -12,6 +12,11 @@ no account and no hidden state.
 **The whole spec.** All four node types (`text`, `file`, `link`, `group`) and
 every edge attribute (`fromSide`/`toSide`, `fromEnd`/`toEnd`, `label`, `color`),
 plus both `canvasColor` forms — the six presets and `#rrggbb` hex.
+The format as this editor reads and writes it is written down in
+[`spec/spec.md`](spec/spec.md), the handful of additions to JSON Canvas 1.0 are
+listed on their own in [`spec/extensions.md`](spec/extensions.md), and the
+original 1.0 spec sits next to them in [`spec/1.0.md`](spec/1.0.md) to diff
+against.
 
 **It does not damage files it does not fully understand.** Unknown top-level
 keys, unknown node/edge attributes and even unknown node `type`s are carried
@@ -43,6 +48,12 @@ Group `background` images are drawn with the fitting their `backgroundStyle`
 asks for (`cover`, `ratio` or `repeat`). Paths are stored relative to the
 canvas, so a canvas plus its files stays portable.
 
+**A display text for link nodes**: name a link in the inspector and the canvas
+shows the name instead of the address, with the full URL in its tooltip. It is
+stored as a `label` attribute — the name groups and edges already use — so a
+tool that does not know about it carries it through untouched. This is an
+addition to the format; see [`spec/extensions.md`](spec/extensions.md).
+
 **The usual editor comforts**: undo/redo of every change, copy/paste/duplicate,
 grouping, alignment, z-order, a properties inspector, snap-to-grid, light and
 dark themes, and a warning before you lose unsaved work.