build core, basic and go variants and add template

template/Containerfile

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+FROM code-basic
+USER root
+ENV HOME=/root
+
+# Install alpine packages
+### 
+### Replace ...  with the alpine packaes you'd like to install.
+### You can browser them on https://pkgs.alpinelinux.org/packages.
+###
+RUN apk add --no-cache ...
+
+# Install neovim plugins
+### 
+### Replace the first ...  with <user>/<repo> strings for every neovim plugin
+### you'd like to install from GitHub. Replace the second ... with a comma
+### separated list of the <repo>s, that contain a doc directory.
+###
+WORKDIR /usr/local/share/nvim/site/pack/plugins/opt
+RUN printf '%s\n' \
+  ... \
+  | xargs -n1 -P0 -I'{}' git clone --depth 1 'https://github.com/{}'
+RUN printf 'helptags %s\n' {...}/doc | nvim --noplugin -es
+
+# Add neovim config
+COPY nvim /etc/xdg/nvim
+
+###
+### Execute further instructions and copy furhter configurations here.
+###
+
+# Configure environment
+USER 1000:1000
+ENV HOME=/tmp