add ADOPTERS.md (#1380)

* add ADOPTERS.md

* add example

Author: SteveL-MSFT

ADOPTERS.md

@@ -0,0 +1,14 @@
+# Adopters
+
+<!--
+Example entry:
+```markdown
+* [PowerShellEditorServices](https://github.com/powershell/powershelleditorservices) uses PowerShell Script Analyzer to provide real-time
+  linting of PowerShell scripts for editors such as [VSCode](https://code.visualstudio.com/), [Neovim](https://neovim.io/), [IntelliJ](https://www.jetbrains.com/idea/), and others.
+```
+-->
+
+This is a list of adopters of using PowerShell Script Analyzer in production or in their products (in alphabetical order):
+
+* [PowerShellEditorServices](https://github.com/powershell/powershelleditorservices) uses PowerShell Script Analyzer to provide real-time
+  linting of PowerShell scripts for editors such as [VSCode](https://code.visualstudio.com/), [Neovim](https://neovim.io/), [IntelliJ](https://www.jetbrains.com/idea/), and others.