v1.9.3

Release v1.9.3

Documentation only - no code changes.

CHANGES
- README, "In a browser": lists the apps that run in a browser today - the showcase
  (https://wolfgang371.github.io/crymbleui/), Minesweeper (https://wolfgang371.github.io/minesweeper/, a small app
  of its own with crymble-ui as a shard - the repository to start a web build from) and Embrace
  (https://h3o.de/demo, a large desktop app, unchanged).
- README: the browser requirement says "tested in Chromium so far", like the showcase link; Firefox and Safari are
  named as supported engines but not yet tried by hand.
- docs/WEB.md: new section "Apps built with it" - the three apps, and what Minesweeper shows a third-party app needs
  for its web build (a shard.yml target, the repository: the page links as its source, Pages publishing).

NOTES
- No code changed since v1.9.2; Windows behaviour is the same as v1.9.2.