Sideloading deprecation (#526)

* Update to note deprecation of sideloading

Ref: https://blog.mozilla.org/addons/2019/10/31/firefox-to-discontinue-sideloaded-extensions/

This change would work best in tandem with the sideloading and registry install articles having a deprecation notice up. I also don't know what docs we have on Enterprise installation.

* Added deprecation notes to some sideloading sections

* Updated phrasing of application installs

* Updated phrasing about application installs

* Fixed phrasing about application installs

documentation/enterprise/enterprise-distribution.md

@@ -83,6 +83,16 @@ You can sideload an add-on using one of the standard extensions folders, as desc
 
 This section explains how to install add-ons into Firefox using the Windows Registry.
 
+{% capture alert %}
+
+Starting in Firefox 73, it will no longer be possible to have an extension be installed automatically as part of another application install. See the [Add-ons Blog](https://blog.mozilla.org/addons/2019/10/31/firefox-to-discontinue-sideloaded-extensions/) for more information.
+
+{% endcapture %}
+{% include modules/note.html
+	content=alert
+	alert=true
+%}
+
 <!-- Alert -->
 
 {% capture alert %}

documentation/publish/distribute-sideloading.md

@@ -5,9 +5,9 @@ permalink: /documentation/publish/distribute-sideloading/
 published: true
 topic: Publish
 tags: [add-on, distribution, sideloading, guide, installation]
-contributors: [irenesmith, jwilk, hellosct1, gray_-_wolf, luanmm, rebloor]
-last_updated_by: hellosct1
-date: 2019-03-18 05:05:42
+contributors: [caitmuenster, irenesmith, jwilk, hellosct1, gray_-_wolf, luanmm, rebloor]
+last_updated_by: caitmuenster
+date: 2019-11-06 04:05:42
 ---
 
 <!-- Page Hero Banner -->
@@ -117,6 +117,20 @@ To use Install Add-on From File in Add-on Manager, send the user the signed add-
 
 ## Installation using the standard extension folders
 
+<!-- Alert -->
+
+{% capture alert %}
+
+Starting in Firefox 73, it will no longer be possible to have an extension be automatically installed as part of another application install. See the [Add-ons Blog](https://blog.mozilla.org/addons/2019/10/31/firefox-to-discontinue-sideloaded-extensions/) for more information.
+
+{% endcapture %}
+{% include modules/note.html
+	content=alert
+	alert=true
+%}
+
+<!-- END: Alert -->
+
 This method of add-on installation involves copying the add-on into one of the standard extension folders on the user's computer. Once copied, the next time Firefox launches the add-on will be installed. By default, the user will be asked to approve the installation, and if the user approves, the add-on will be installed and automatically loaded for subsequent launches. If the user has more than one Firefox profile, the approval and installation will occur on the next launch of each profile. For details on controlling whether the user is prompted to approve the installation, see [Controlling automatic installation](/documentation/enterprise/enterprise-distribution/#controlling-automatic-installations).
 
 ### Rename your XPI file