[Docker] Install Python3 on Alpine Linux

By default Python is not installed on Alpine Linux, if you want to install Python3 you can make use of the apk add command,

# apk add --update python3

fetch https://dl-cdn.alpinelinux.org/alpine/v3.15/main/aarch64/APKINDEX.tar.gz
fetch https://dl-cdn.alpinelinux.org/alpine/v3.15/community/aarch64/APKINDEX.tar.gz
(1/10) Installing libbz2 (1.0.8-r1)
(2/10) Installing expat (2.4.7-r0)
(3/10) Installing libffi (3.4.2-r1)
(4/10) Installing gdbm (1.22-r0)
(5/10) Installing xz-libs (5.2.5-r1)
(6/10) Installing libgcc (10.3.1_git20211027-r0)
(7/10) Installing libstdc++ (10.3.1_git20211027-r0)
(8/10) Installing mpdecimal (2.5.1-r1)
(9/10) Installing sqlite-libs (3.36.0-r0)
(10/10) Installing python3 (3.9.7-r4)
Executing busybox-1.34.1-r5.trigger
OK: 56 MiB in 28 packages