docs: notice about semver and data sources (#330)

README.md

@@ -54,6 +54,12 @@ Each mime type has the following properties:
 
 If unknown, every property could be `undefined`.
 
+## Note on MIME Type Data and Semver
+
+This package considers the programmatic api as the semver compatibility. This means the MIME type resolution is *not* considered
+in the semver bumps. This means that if you want to pin your `mime-db` data you will need to do it in your application. While
+this expectation was not set in docs until now, it is how the pacakge operated, so we do not feel this is a breaking change.
+
 ## Contributing
 
 The primary way to contribute to this database is by updating the data in