Add best practices to Solutions (#37489)

So we don't forget.

docs/solutions/README.md

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+# Solutions Best Practices
+
+
+## General
+
+– Name the file what the profile does.
+  - For example, instead of `googlePlayProtectVerifyApps.json` (the name of the
+    Android policy for this control), describe what it does:
+    `enforce-google-play-protect.json`.
+– Use kebab case in file names, with all letters in lowercase.
+  - Instead of `passwordPolicy.json`, use `password-policy.json`.
+– Be sure to end files with an empty newline.