Mention Docker 20.10 in the changelog

CHANGELOG.md

@@ -1,3 +1,15 @@
+# 2020-12-11
+
+## Docker 20.10 is here
+
+(No need to do anything special in relation to this. Just something to keep in mind)
+
+Docker 20.10 got released recently and your server will likely get it the next time you update.
+
+This is the first major Docker update in a long time and it packs a lot of changes.
+Some of them introduced some breakage for us initially (see [here](https://github.com/spantaleev/matrix-docker-ansible-deploy/commit/d08b27784f222effcbce2abf924bf07bbe0893be) and [here](https://github.com/spantaleev/matrix-docker-ansible-deploy/commit/7593d969e316cc0144bce378a5be58c76c2c37ee)), but it should be all good now.
+
+
 # 2020-12-08
 
 ## openid APIs exposed by default on the federation port when federation disabled