Create a doc for adding common third-party tools (#3353)

* Create a doc for adding common third-party tools

Maybe it would be helpful to have a comprehensive guide on adding some common third-party tools as profiles.

* add some additional tools from PR

doc/user-docs/ThirdPartyToolProfiles.md

@@ -0,0 +1,67 @@
+# Adding profiles for third-party tools
+
+This doc will hopefully provide a useful guide for adding profiles for common
+third-party tools to your
+[profiles.json](https://github.com/microsoft/terminal/blob/master/doc/user-docs/UsingJsonSettings.md)
+file.
+
+All of these profiles are provided _without_ their `guid` set. If you'd like to
+set any of these profiles as your _default_ profile, you'll need to make sure to
+[generate a unique guid](https://www.guidgenerator.com/) for them manually.
+
+## Anaconda
+
+Assuming that you've installed Anaconda into `%USERPROFILE%\Anaconda3`:
+
+```json
+{
+    "commandline" : "cmd.exe /K %USERPROFILE%\\Anaconda3\\Scripts\\activate.bat %USERPROFILE%\\Anaconda3",
+    "icon" : "%USERPROFILE%/Anaconda3/Menu/anaconda-navigator.ico",
+    "name" : "Anaconda3",
+    "startingDirectory" : "%USERPROFILE%"
+}
+```
+
+## cmder
+
+Assuming that you've installed cmder into `%CMDER_ROOT%`:
+
+```json
+{
+    "commandline" : "cmd.exe /k %CMDER_ROOT%\\vendor\\init.bat",
+    "name" : "cmder",
+    "startingDirectory" : "%USERPROFILE%"
+}
+```
+
+## Cygwin
+
+Assuming that you've installed Cygwin into `C:/Cygwin`:
+
+```json
+{
+    "name" : "Cygwin",
+    "commandline" : "C:/Cygwin/bin/bash --login -i",
+    "icon" : "C:/Cygwin/Cygwin.ico",
+    "startingDirectory" : "C:/Cygwin/bin"
+}
+```
+
+Note that the starting directory of Cygwin is set as it is to make the path
+work. The default directory opened when starting Cygwin will be `$HOME` because
+of the `--login` flag.
+
+## Git Bash
+
+Assuming that you've installed Git Bash into `C:/Program Files/Git`:
+
+```json
+{
+    "name" : "Git Bash",
+    "commandline" : "C:/Program Files/Git/bin/bash.exe",
+    "icon" : "C:/Program Files/Git/mingw64/share/git/git-for-windows.ico",
+    "startingDirectory" : "%USERPROFILE%"
+}
+````
+
+<!-- Adding a tool here? Make sure to add it in alphabetical order! -->