Add categories to docs

Author: tsolomko

.jazzy.yaml

@@ -9,3 +9,18 @@ readme: README.md
 github_url: https://github.com/tsolomko/BitByteData
 github_file_prefix: https://github.com/tsolomko/BitByteData/tree/develop
 theme: fullwidth
+
+custom_categories:
+    - name: Reading bytes
+      children:
+      - ByteReader
+    - name: Reading bits (and bytes)
+      children:
+      - BitReader
+      - LsbBitReader
+      - MsbBitReader
+    - name: Writing bits (and bytes)
+      children:
+      - BitWriter
+      - LsbBitWriter
+      - MsbBitWriter