Allow manifest.encodings to be an object

Author: vweevers

README.md

@@ -353,9 +353,19 @@ Does db have the methods `createReadStream`, `createKeyStream` and `createValueS
 
 </details>
 
-### `encodings` (boolean)
+### `encodings` (boolean or object)
 
-Do all relevant db methods take `keyEncoding` and `valueEncoding` options? If true, the db must use a default encoding of utf8 and all its operations must return strings rather than buffers by default.
+Do all relevant db methods take `keyEncoding` and `valueEncoding` options? If truthy, the db must use a default encoding of utf8 and all its operations must return strings rather than buffers by default.
+
+Support of individual encodings may also be indicated by adding their names as nested properties. For example:
+
+```js
+{
+  encodings: {
+    utf8: true
+  }
+}
+```
 
 <details>
 <summary>Support matrix</summary>

index.js

@@ -31,7 +31,7 @@ module.exports = function supports (...manifests) {
     openCallback: manifest.openCallback || false,
     promises: manifest.promises || false,
     streams: manifest.streams || false,
-    encodings: manifest.encodings || false,
+    encodings: maybeObject(manifest.encodings),
     events: maybeObject(manifest.events),
 
     // Methods that are not part of abstract-leveldown or levelup