Adds a makefile

Makefile

+# Use this makefile in Linux to build and serve the local development environment
+# with one command.
+# Please make sure to have Jekyll and ffmpeg installed
+
+.PHONY: all install clean serve install-dependencies install-submodules jumbotrons
+
+all: install jumbotrons serve
+
+install: install-dependencies install-submodules
+
+serve:
+	bundle exec jekyll serve --future
+
+clean:
+	rm -rf assets/img/jumbotrons/desktop
+	rm -rf assets/img/jumbotrons/display_2k
+	rm -rf assets/img/jumbotrons/phone
+	rm -rf assets/img/jumbotrons/tablet
+	rm -rf .jekyll-cache
+	rm -rf _site
+
+install-dependencies: Gemfile Gemfile.lock
+	bundle install
+
+install-submodules: .gitmodules
+	git submodule update --init --recursive
+
+jumbotrons:
+	bash scripts/create_jumbotrons.sh assets/img/jumbotrons/

README.md

@@ -6,6 +6,8 @@ is built using Jekyll.
 
 ## Build the project locally
 
+### Manually
+
 1. Clone the project locally
    ```bash
    git clone --recursive https://gitlab.hzdr.de/hifis/hifis.net.git
@@ -48,7 +50,26 @@ Execute the commands above from the root of your repository.
 More information is available in Jekyll's
 [documentation](https://jekyllrb.com/docs/)
 
+### Using the Makefile
+
+If you are using Linux, you may also use the provided `Makefile`. After having
+cloned the repository (Step 1 above), make sure to have Jekyll and ffmpeg installed.
+Now you can start the local development server by running
+
+```shell
+make all
+```
+
+Individual steps can also be called:
+
+```shell
+make install     # install dependencies and update submodule
+make jumbotrons  # build the jumbotrons using ffmpeg
+make serve       # start the dev server
+make clean       # Remove all generated/downloaded files
+```
+
 ## Fetch the latest builds from gitlab
 
 The latest master branch (production) build artifacts can be downloaded using
-* https://gitlab.hzdr.de/hifis/hifis.net/-/jobs/artifacts/master/download?job=build:production 
+* https://gitlab.hzdr.de/hifis/hifis.net/-/jobs/artifacts/master/download?job=build:production