Tidy up and remove unused things (#464)

- The Docker stuff had broken and with no tests/uncertain uses
  I decided to remove it. We can resurrect if useful (cc @pacman-ghost)
- Delete some unused icons
- Fix up the prettier ignore

Author: mattgodbolt

.prettierignore

@@ -1,4 +1,4 @@
-out
+dist
 tests/6502_65C02_functional_tests
 tests/integration/dp111_6502Timing
 package-lock.json