Add 'unzip' to the tools installed in Dev Container

[kio-watanabe]

'-m' test of command-line options within the Dev Container environment failed due to the absence of 'unzip'. Therefore, I modified the Dockerfile to include the installation of 'unzip'.

test log:

#                             -*- compilation -*-
7. m.at:1: testing -m ...
./m.at:12: touch hello.txt
./m.at:14: ${COBJ} -m prog.cbl
./m.at:15: CLASSPATH=$CLASSPATH:./prog.jar java prog
./m.at:19: mkdir tmp && mv prog.jar tmp && cd tmp && unzip prog.jar > /dev/null
--- /dev/null	2024-11-19 00:53:10.830684202 +0000
+++ /workspaces/opensourcecobol4j/tests/command-line-options.dir/at-groups/7/stderr	2024-11-19 00:55:57.589857026 +0000
@@ -0,0 +1 @@
+/workspaces/opensourcecobol4j/tests/command-line-options.dir/at-groups/7/test-source: line 66: unzip: command not found
./m.at:19: exit code was 127, expected 0
7. m.at:1: 7. -m (m.at:1): FAILED (m.at:19)