Add RELEASE-NOTES for next release (#4046)

* Add RELEASE-NOTES template for next

The placeholder items are useful instead of having to find the •
character for every new release.

Closes #4040

* Remove leftover bugfix release notes from tree

RELEASE-NOTES-next

@@ -0,0 +1,34 @@
+
+ ┌──────────────────────────────┐
+ │ Release notes for i3 v4.19   │
+ └──────────────────────────────┘
+
+This is i3 v4.19. This version is considered stable. All users of i3 are
+strongly encouraged to upgrade.
+
+ ┌────────────────────────────┐
+ │ Changes in i3 v4.19        │
+ └────────────────────────────┘
+
+  • configure: respect --program-suffix
+  • use exec to avoid leaving useless shell process
+  • ipc: always include the marks property (even if empty)
+  • introduce “tiling_from” and ”floating_from” criteria
+  • make dock client order deterministic (sorted by class/instance) as a
+    side effect, i3bars without an explicit bar-id will be sorted according
+    to their definition order in the config file
+
+ ┌────────────────────────────┐
+ │ Bugfixes                   │
+ └────────────────────────────┘
+
+  • ensure client windows have a size of at least 1px after resize
+  • correctly handle overlapping decorations
+  • limit workspace numbers within 0..INT32_MAX
+  • fix a bug with tiling resize inside floating container
+  • i3-nagbar: Use _PATH_BSHELL to ensure using a bourne shell
+  • do not propagate $mod+right click to fullscreen clients
+  • do not try to resize fullscreen and non-fullscreen windows
+  • do not focus floating windows changing workspace with ConfigureNotify
+  • i3-dmenu-desktop: Support symlinks in search path
+  • build: correctly provide auxiliary functions when needed