Add initial CHANGELOG for v2.6.0

Author: sim642

CHANGELOG.md

@@ -1,3 +1,19 @@
+## v2.6.0 Awkward Aardvark (unreleased)
+* Add division by zero analysis (#1764).
+* Add bitfield domain (#1623).
+* Add weakly-relational C-2PO pointer analysis (#1485).
+* Add widening delay (#1358, #1442, #1483).
+* Add narrowing of globals to top-down solver (#1636).
+* Add weak dependencies to top-down solver (#1746, #1747).
+* Add YAML ghost witness generation (#1394).
+* Use C standard option for preprocessing (#1807).
+* Add bash completion for array options (#1670, #1705, #1750).
+* Make `malloc(0)` semantics configurable (#1418, #1777).
+* Update path-sensitive analyses (#1785, #1791, #1792).
+* Fix evaluation of library function arguments (#1758, #1761).
+* Optimize affine equalities analysis using sparse matrices (#1459, #1625).
+* Prepare for parallelism (#1708, #1744, #1748).
+
 ## v2.5.0
 Functionally equivalent to Goblint in SV-COMP 2025.