Suggest improvements in my snap's .yaml file

Hey there,
Here’s my snapcraft.yaml file:

name: readaratus
version: ‘2.1’
summary: A dynamic book reading system for computers
license: GPL-3.0+
grade: stable
description:
base: core18
confinement: strict

slots:
dbus-daemon:
interface: dbus
bus: session
name: org.readaratus.decoder

parts:
readaratus:
plugin: dump
source: https://github.com/rezahsnz/readaratus/releases/download/v2.1/readaratus-$SNAPCRAFT_PROJECT_VERSION-64bit-Linux.tar.gz
stage-packages: [libpoppler-glib8]

apps:
readaratus:
command: readaratus
extensions: [gnome-3-28]
slots: [dbus-daemon]
plugs:
- home
- desktop
- desktop-legacy
- wayland
- unity7

Since I am new to snapping, I do not fully understand its inner workings and I hope to get some help. I am specially interested in decreasing my snap’s download size which is around 8MB while my application is only 300KB. My app is basically an Ebook reader based on Gtk3 and Poppler-glib.
Please take some time and feel free in suggesting any improvements that you think is necessary.