Add sqlite3 to dockerfile

Dockerfile

@@ -1,7 +1,7 @@
 FROM python:3.8.3-slim-buster
 
 RUN apt-get update \
-    && apt-get -y install curl build-essential libssl-dev \
+    && apt-get -y install curl build-essential libssl-dev sqlite3 \
     && apt-get clean \
     && pip install --upgrade pip
 

Dockerfile.armhf

@@ -1,7 +1,7 @@
 FROM --platform=linux/arm/v7 python:3.7.7-slim-buster
 
 RUN apt-get update \
-  && apt-get -y install curl build-essential libssl-dev libatlas3-base libgfortran5 \
+  && apt-get -y install curl build-essential libssl-dev libatlas3-base libgfortran5 sqlite3 \
   && apt-get clean \
   && pip install --upgrade pip \
   && echo "[global]\nextra-index-url=https://www.piwheels.org/simple" > /etc/pip.conf

docs/sql_cheatsheet.md

@@ -13,6 +13,15 @@ Feel free to use a visual Database editor like SqliteBrowser if you feel more co
 sudo apt-get install sqlite3
 ```
 
+### Using sqlite3 via docker-compose
+
+The freqtrade docker image does contain sqlite3, so you can edit the database without having to install anything on the host system.
+
+``` bash
+docker-compose exec freqtrade /bin/bash
+sqlite3 <databasefile>.sqlite
+```
+
 ## Open the DB
 
 ```bash