Add extension screenshots for learn

learn/develop-cloud/containers.md

@@ -29,6 +29,8 @@ In the diagram below, you'll see an example of 3 dev containers: one for Python,
 
 To get started with using dev containers in VS Code, you'll need to download the [Remote - Containers extension](https://marketplace.visualstudio.com/items?itemName=ms-vscode-remote.remote-containers) from the Extension Marketplace.
 
+<img src="images/remote-containers.png" alt="Remote Containers extension" aria-hidden="true" class="thumb"/>
+
 You'll also need to download [Docker](https://docs.docker.com/docker-for-windows/install-windows-home/), which is the industry standard for building and sharing containers.
 
 ### Sample dev containers

learn/develop-cloud/images/remote-containers.png

@@ -0,0 +1,3 @@
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+oid sha256:c995cf71b48569cb6b9d8b341fdda2bbbe05a96c89372d70335b6464099dd3f7
+size 124247

learn/develop-cloud/images/remote-ssh.png

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:c77a24b93400ca2660dd1d50d30ed64b4b80f398d8c90e43d0da834b0081a4cd
+size 86257

learn/develop-cloud/images/remote-wsl.png

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:90195cd0bdbb622255c958036a31f7306d8fd85bc0d5849eca2d9d240207a800
+size 136804

learn/develop-cloud/ssh-lab-machines.md

@@ -23,6 +23,8 @@ In the classroom, you might SSH into lab machines to access computers with certa
 
 To get started with using SSH in VS Code, you'll need to download the [Remote - SSH extension](https://marketplace.visualstudio.com/items?itemName=ms-vscode-remote.remote-ssh) from the Extension Marketplace.
 
+<img src="images/remote-ssh.png" alt="Remote SSH extension" aria-hidden="true" class="thumb"/>
+
 Check out the following video to see an example of using Remote - SSH in action:
 
 <iframe src="https://youtube.com/embed/rh1Ag41J6IA?rel=0&amp;disablekb=0&amp;modestbranding=1&amp;showinfo=0" frameborder="0" allowfullscreen></iframe>

learn/develop-cloud/wsl.md

@@ -18,6 +18,8 @@ WSL especially helps web developers and those working with Bash and Linux-first
 
 To get started with using WSL in VS Code, you'll need to download the [Remote - WSL extension](https://marketplace.visualstudio.com/items?itemName=ms-vscode-remote.remote-wsl) from the Extension Marketplace.
 
+<img src="images/remote-wsl.png" alt="Remote WSL extension" aria-hidden="true" class="thumb"/>
+
 You'll also need WSL and a distro installed. We recommend using WSL 2, which is the newest version of WSL, as you will benefit from significant [performance advantages](https://docs.microsoft.com/en-us/windows/wsl/compare-versions) over WSL 1.
 
 Check out Remote - WSL in action: