Add script to install dependencies on Debian/Ubuntu.

Tested with Xubuntu 20.04 and Debian testing
(in today's Docker image bitnami/minideb).

Update README.md.

dist/get_deps_debian.sh

@@ -0,0 +1,29 @@
+#!/usr/bin/env sh
+
+echo "As of 2020-12, Debian stable does not include g++-10, needs debian testing or unstable."
+
+# Tested on 2020-12-09 with Docker image bitnami/minideb:unstable
+
+# Install pkgconf (adds minimum dependencies) only if the equivalent pkf-config is not already installed.
+if !which pkg-config
+then
+    PKGCONF="pkgconf"
+fi
+
+apt install \
+  cmake \
+  g++-10 \
+  ${PKGCONF:-} \
+  nlohmann-json3-dev \
+  libcapstone-dev \
+  libmagic-dev \
+  libglfw3-dev \
+  libglm-dev \
+  libjsoncpp-dev \
+  llvm-dev \
+  libssl-dev \
+  libstdc++-10-dev \
+  python3-dev
+
+echo "Please consider this before running cmake (useful on e.g. Ubuntu 20.04):"
+echo "export CXX=g++-10"