Merge pull request #39 from StephanieSu/patch-2

Mention Core editor as bare minimum prereq

Author: Greg Van Liew

docs/extensibility/how-to-migrate-extensibility-projects-to-visual-studio-2017.md

@@ -72,6 +72,8 @@ To update the NuGet references to Microsoft.VSSDK.BuildTools:
 
 To ensure that the user's installation of Visual Studio has all the assemblies required to run the extension, specify all the prerequisite components or packages in the extension manifest file. When a user attempts to install the extension, the VSIXInstaller will check to see if all the prerequisites are installed. If some are missing, the user will be prompted to install the missing components as part of the extension installation process.
 
+>**Note:** At a minimum, all extensions should specify the Visual Studio core editor component as a prerequisite.
+
 * Edit the extension manifest file (usually called source.extension.vsixmanifest).
 * Ensure `InstallationTarget` includes 15.0.
 * Add required installation prerequisites (as shown in the example below).
@@ -209,4 +211,4 @@ For all your references, first determine which ones are in the core editor (Micr
 Examples:
 
 * If you have a debugger extension and know that your project has a reference to VSDebugEng.dll and VSDebug.dll, click on the filter button in the **Binaries / Files Names** header.  Search for "VSDebugEng.dll" and select OK.  Next click on the filter button in the **Binaries / Files Names** header again and search for "VSDebug.dll".  Select the checkbox "Add current selection to filter" and select OK.  Now look through the **Component Name** to find a component that is most related to your extension type. In this example, you would chose the Just-In-Time debugger and add it to your vsixmanifest.
-* If you know that your project deals with debugger elements, you can search on "debugger" in the filter search box to see what components contain debugger in its name.
+* If you know that your project deals with debugger elements, you can search on "debugger" in the filter search box to see what components contain debugger in its name.