Assert removable-media interface in the snap

This allows access to the files under `/media/*` and `/run/media/*`, as
the connection is not automatic connect instructions is also added to
the snap's description.

Refer-to: Interfaces - doc - snapcraft.io
<https://forum.snapcraft.io/t/interfaces/6154>
Signed-off-by: 林博仁(Buo-ren, Lin) <Buo.Ren.Lin@gmail.com>

snap/snapcraft.yaml

@@ -6,6 +6,11 @@ description: |
   languages "out of the box". It can be trained to recognize other languages.
   Tesseract supports various output formats: plain-text, hocr(html), pdf.
 
+  If you want to access the files under /media/* or /run/media/* you'll have
+  to connect the snap to the `core` snap's `removable-media` interface:
+
+      $ sudo snap connect tesseract:removable-media
+
 grade: stable # must be 'stable' to release into candidate/stable channels
 confinement: strict
 
@@ -15,7 +20,9 @@ apps:
       env
       TESSDATA_PREFIX=$SNAP_USER_COMMON
       tesseract
-    plugs: [home]
+    plugs:
+      - home
+      - removable-media
 
 parts:
   tesseract: