Update CHANGES v14

Author: knorrie

CHANGES

@@ -1,3 +1,20 @@
+python-btrfs v14, Apr 28, 2024
+  * Add Block Group Tree support.
+  * Add a block_groups convenience function to the FileSystem class.
+  * btrfs-search-metadata: Use the new FileSystem block_groups function, so
+    that it also DTRT when the Block Group Tree is being used.
+  * Fixes:
+    - Do not apply the workaround to prevent bogus cross references when
+      building documentation with Sphinx version >= 4. It's not needed any more
+      since that version. Thanks Jorti, for the report.
+    - Fix documentation typo in FeatureFlags: free_space_tree is in
+      compat_ro_flags, not in incompat_flags.
+    - examples/show_file_csum: Fix calculating the vaddr to use when searching
+      for data in the example file. Thanks Cebtenzzre, for the fix!
+  * Stuff:
+    - Add a .flake8 file to set line length to 99
+    - Add .readthedocs.yaml to fix building html docs at readthedocs.org
+
 python-btrfs v13, Apr 26, 2021
   * Add new profiles RAID1C3 and RAID1C4. Thanks, Marmotte.
   * Update setup.py so that the package description is more compact and not