Release notes for 8.0.0-beta1 (elastic#13373)

* Update release notes for 8.0.0

* Add Java 11 minimum breaking change
* Add feature-level headings for scanability
* Add link to breaking changes
* Add note about plugin alignment

Co-authored-by: João Duarte <jsvd@users.noreply.github.com>
Co-authored-by: Rob Bavey <rob.bavey@elastic.co>
Co-authored-by: Karen Metts <karen.metts@elastic.co>

docs/static/releasenotes.asciidoc

@@ -12,7 +12,53 @@ This section summarizes the changes in the following releases:
 [[logstash-8-0-0-beta1]]
 === Logstash 8.0.0-beta1 Release Notes
 
-coming[8.0.0-beta1]
+==== Breaking changes
+
+[[rn-java-11-minimum]]
+===== Java 11 minimum
+Starting from Logstash 8.0, the minimum required version of Java to run Logstash is Java 11. By default, Logstash will
+run with the bundled JDK, which has been verified to work with each specific version of Logstash, and generally
+provides the best performance and reliability.
+
+See <<breaking-changes>> for a preview of additional breaking changes coming your way. 
+
+==== New features and enhancements
+
+[[rn-nanosecond-precision]]
+===== Nanosecond precision
+As processing times speed up, millisecond granularity is not always enough. Inbound data increasingly has sub-millisecond granularity timestamps.
+The pull request https://github.com/elastic/logstash/pull/12797[#12797] allows the internal mechanisms of Logstash that hold moment-in-time data - such as the Logstash Event, the Persistent Queue, the Dead Letter Queue and JSON encoding/decoding - to have nanosecond granularity.
+
+Timestamp precision is limited to the JVM and Platform's available granularity, which in many cases is microseconds.
+
+This change also grants users access to https://docs.oracle.com/javase/8/docs/api/java/time/format/DateTimeFormatter.html#patterns[Java time's improved formatters], which include support fort ISO quarters, week-of-month, and a variety of timezone/offset-related format substitutions. For example:
+
+[source,json]
+--------------------------------------------------------------------------------
+filter {
+  mutate {
+    add_field => {"nanos" => "Nanos: %{{n}}" }
+  }
+}
+--------------------------------------------------------------------------------
+
+Results in the following event:
+
+[source,json]
+--------------------------------------------------------------------------------
+{
+    "@timestamp" => 2021-10-31T22:32:34.747968Z,
+          "host" => "logstash.lan",
+         "nanos" => "Nanos: 747968000",
+       "message" => "test",
+          "type" => "stdin",
+      "@version" => "1"
+}
+--------------------------------------------------------------------------------
+
+==== Plugin releases
+Plugins align with release 7.15.1
+
 
 [[logstash-8-0-0-alpha2]]
 === Logstash 8.0.0-alpha2 Release Notes
@@ -57,4 +103,4 @@ We have added another flag to the Benchmark CLI to allow passing a data file wit
 This feature allows users to run the Benchmark CLI in a custom test case with a custom config and a custom dataset. https://github.com/elastic/logstash/pull/12437[#12437]
 
 ==== Plugin releases
-Plugins align with release 7.14.0
+Plugins align with release 7.14.0