added a summary of BOLTs PR 918

Of course one can argue whether this is a notable code change.
I think this feature is very useful for LSPs and it seemed to be heavily motivated from that context by Matt. As Optech reader are mainly professionals I thought I should at least suggest to write about the update.

Author: lightning-developer

_posts/en/newsletters/2021-12-15-newsletter.md

@@ -97,6 +97,14 @@ repo], [Hardware Wallet Interface (HWI)][hwi repo],
   merged this week, updates that implementation to follow this updated
   specification.
 
+- [BOLTs #918][] removes the rate limiting of ping messages. `ping` messages
+  are mainly used to check if the peer connection is still alive. Prior to
+  this merge `ping` messages were supposed to be sent at most once every 30
+  seconds. For many nodes it is useful to send heart beat messages via `ping`
+  more frequently to assure a high quality of service. As other  Lightning 
+  messages are not rate limited the 30 seconds rate limit for `ping` messages
+  was also dropped.
+
 - [BOLTs #906][] introduce feature bit to gate new channel_type feature FIXME:dongcarl
 
 ## Holiday publication schedule
@@ -107,7 +115,7 @@ return to regular publication on Wednesday, January 5th.
 
 <!-- FIXME:harding update topics/releases/RCs -->
 {% include references.md %}
-{% include linkers/issues.md issues="867,23716,20295,14707,23486,940,906,1204" %}
+{% include linkers/issues.md issues="867,23716,20295,14707,23486,940,906,1204,918" %}
 [news162 unec]: /en/newsletters/2021/08/18/#dust-limit-discussion
 [rubin unec]: https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2021-December/019635.html
 [somsen unec]: https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2021-December/019637.html