Changes to dockerfile + more intricate .emacs file

Dockerfile

@@ -1,10 +1,21 @@
 FROM debian
 
+# install emacs + clang + clangd as LSP.
 ENV DEBIAN_FRONTEND=noninteractive
 
 RUN apt update && \
-    apt install -y emacs clang clangd && \
-    apt clean all
+    apt install -y emacs build-essential git make cmake clang clang-format clangd && \
+    apt clean all && \
+    rm -rf /var/lib/apt/lists/*
+
+# copy emacs config
+COPY emacs-init /root/.emacs
+
+# install emacs packages by running once beforehand,
+# so we don't have to that every start-up
+RUN emacs --batch -l /root/.emacs \
+    --eval "(package-refresh-contents)" \
+    --eval "(package-install-selected-packages)"
 
 
-ENTRYPOINT ["/bin/emacs" "-nw"]
+ENTRYPOINT ["/bin/emacs", "-nw"]