update change log for 0.7

CHANGELOG.rst

 Change Log
 ==========
 
+0.7.0: 2021/01/07
+-----------------
+
+* converter
+    * hdf5: management of ExternalLink as entry (case of bliss proposal file, PR 85)
+    * edf
+        * fix issues with progress (PR 80)
+
+* patch-nx
+    * add option to convert all frame of a given type (PR 84)
+
+* dxfile2nx
+    * allow to provide pixel size as a single value (PR 77)
+
+* miscellaneous::
+    * add some missing aliases flat/ref (PR 83)
+    * benefit from validator (PR 81)
+
+
 0.6.0: 2021/10/04
 -----------------