* Add duktape-clang-format Docker image with clang-format-12.
* Add Makefile target docker-image-clang-format to build the image,
and clang-format-source to format src-input sources in-place.
* No CI integration or automation yet, .clang-format is also a
placeholder.
Update Node.js in Docker base images to 14.x from 10.x.
Also add duktape-make-xxx to simplify docker setup. Arbitrary make
commands can be executed with the duktape-make-xxx image. Results
written to build/, dist/, and tmp/ are unpacked to the host work directory.
* Use emscripten-core/emsdk for emcc init.
* Better emcc cache warming in init so that emcc targets then build
without compiling library bc files.
* Reduce I/O for STDIN_ZIP case by copying duktape-releases from repo
snapshots.
* Use /work instead of /build inside Docker image.
* If /work/duktape exists, use it as is. This is useful if docker
call site mounts /work/duktape manually.
* Add GCC and Clang versions to docker base image, and some small
useful packages.
* Add a 'shell' image for testing stuff in a container.
* Run as non-root in Docker containers.
* Colorized prompts to distinguish in-docker vs. out-of-docker easily.
* Gitignore and Makefile updates. Add 'docker-clean' Makefile target
to delete images. Add 'docker-shell-master' and
'docker-shell-wdmount' targets to use the shell container.
* Short README entry on Docker images.
* Add Makefile target 'docker-images' to build the images, in the
desired order.
* Add Makefile targets and Docker images for source and website dist
from (public) master.
* Trivial .gitignore update.
* duktape-base-ubuntu-18.04: Base image suitable for all Duktape
compilation, test runs, website builds, etc. Ubuntu 18.04.xx is
LTS and supported until 2028.
* Trivial .gitignore update.