Add 2021.1 release blurb (PR #12376)

Co-authored-by: Reef Turner <feerrenrut@users.noreply.github.com>
Co-authored-by: Bill Dengler <codeofdusk@gmail.com>

user_docs/en/changes.t2t

@@ -4,6 +4,15 @@ What's New in NVDA
 %!includeconf: ../changes.t2tconf
 
 = 2021.1 =
+This release includes optional experimental support for UIA in Excel and Chromium browsers.
+There are fixes for several languages, and for accessing links in Braille.
+There are updates to Unicode CLDR and mathematical symbols, eSpeak-NG and LibLouis.
+
+Many bug fixes and improvements, including in Office, Visual Studio and several languages.
+Note: this is an Add-on API compatibility breaking release.
+Add-ons will need to be re-tested and have their manifest updated.
+This release also drops support for Adobe Flash.
+
 
 == New Features ==
 - Early support for UIA with Chromium based browsers (such as Edge). (#12025)
@@ -49,7 +58,7 @@ What's New in NVDA
    - known issue for right-to-left languages: the right border of groupings clips with labels/controls. (#12181)
 - The python locale is set to match the language selected in preferences consistently, and will occur when using the default language. (#12214)
 - - TextInfo.getTextInChunks no longer freezes when called on Rich Edit controls such as the NVDA log viewer. (#11613)
-- It is once again possible to use NVDA in a languages containing underscores in the locale name such as de_CH on Windows 10 1803 and 1809. (#12250)
+- It is once again possible to use NVDA in languages containing underscores in the locale name such as de_CH on Windows 10 1803 and 1809. (#12250)
 - In WordPad, configuration of superscript/subscript reporting works as expected. (#12262)
 - NVDA no longer fails to announce the newly focused content on a web page if the old focus disappears and is replaced by the new focus in the same position. (#12147)
 - Strikethrough, superscript and subscript formatting for entire Excel cells are now reported if the corresponding option is enabled. (#12264)
@@ -61,7 +70,7 @@ What's New in NVDA
 
 
 == Changes for Developers ==
-- Note: this is a Add-on API compatibility breaking release. Add-ons will need to be re-tested and have their manifest updated.
+- Note: this is an Add-on API compatibility breaking release. Add-ons will need to be re-tested and have their manifest updated.
 - NVDA's build system now fetches all Python dependencies with pip and stores them in a Python virtual environment. This is all done transparently.
  - To build NVDA, SCons should continue to be used in the usual way. E.g. executing scons.bat in the root of the repository. Running ``py -m SCons``  is no longer supported, and ``scons.py`` has also been removed. 
  - To run NVDA from source, rather than executing ``source/nvda.pyw`` directly, the developer should now use ``runnvda.bat`` in the root of the repository. If you do try to execute ``source/nvda.pyw``, a message box will alert you this is no longer supported.