Add release note section for 2.15

CHANGELOG.txt

@@ -1,6 +1,12 @@
 Changelog
 =========
 
+2.15 (xx.xx.xxxx) - IN DEVELOPMENT
+~~~~~~~~~~~~~~~~~
+
+ * ...
+
+
 2.14 (xx.xx.xxxx) - IN DEVELOPMENT
 ~~~~~~~~~~~~~~~~~
 

docs/releases/2.15.rst

@@ -0,0 +1,26 @@
+===========================================
+Wagtail 2.15 release notes - IN DEVELOPMENT
+===========================================
+
+.. contents::
+    :local:
+    :depth: 1
+
+Wagtail 2.15 is designated a Long Term Support (LTS) release. Long Term Support releases will continue to receive maintenance updates as necessary to address security and data-loss related issues, up until the next LTS release (typically a period of 12 months).
+
+
+What's new
+==========
+
+Other features
+~~~~~~~~~~~~~~
+
+ * ...
+
+Bug fixes
+~~~~~~~~~
+
+ * ...
+
+Upgrade considerations
+======================

docs/releases/index.rst

@@ -5,6 +5,7 @@ Release notes
    :maxdepth: 1
 
    upgrading
+   2.15
    2.14
    2.13.4
    2.13.3

docs/releases/upgrading.rst

@@ -145,3 +145,5 @@ The compatible versions of Django and Python for each Wagtail release are:
 +-------------------+------------------------------+-----------------------------+
 | 2.14              | 3.0, 3.1, 3.2                | 3.6, 3.7, 3.8, 3.9          |
 +-------------------+------------------------------+-----------------------------+
+| 2.15 LTS          | 3.0, 3.1, 3.2                | 3.6, 3.7, 3.8, 3.9          |
++-------------------+------------------------------+-----------------------------+