feat: Dockerfile for reproducible dev/ci environment

Author: fjfnaranjo

CONTRIBUTING.md

@@ -135,6 +135,15 @@ make colors-check
 
 This is run in CI and ensures that generation was correct by re-running it and validating that no changes were made.
 
+### Using the local container image
+
+You can build and use the included container image to run the previous commands.
+
+```sh
+docker build -t nvim-web-devicons:latest .
+docker run --rm -ti --user "`id -u`:`id -g`" -v "$(pwd):/host" -w /host nvim-web-devicons:latest make
+```
+
 ## Test
 
 Run `:NvimWebDeviconsHiTest` to view the icons and their highlighting.

Dockerfile

@@ -0,0 +1,18 @@
+FROM debian:stable-slim
+
+ENV DEBIAN_FRONTEND=noninteractive
+
+RUN apt-get update \
+ && apt-get install -y --no-install-recommends \
+    make gcc curl npm luarocks git \
+ && rm -rf /var/lib/apt/lists/*
+
+# Neovim
+RUN curl -L 'https://github.com/neovim/neovim/releases/download/stable/nvim-linux-x86_64.tar.gz' \
+    | tar zx --directory /usr --strip-components=1
+
+## luacheck
+RUN luarocks install luacheck
+
+# stylua wrapper (npx to avoid cargo deps)
+RUN npm install --global @johnnymorganz/stylua-bin