Add license and basic documentation

LICENSE:
Add GPL-3.0 license.

{{archiso,configs}/*,.editorconfig,.gitlab-ci.yml}:
Add SPDX license identifier.

Makefile:
Add SPDX license identifier.
Install the `run_archiso.sh` script as global executable `run_archiso`.
Use -D and -t flags to install to install files more generically (without a previous call to install the directory).

README.rst:
Add README outlining the project's scope, how to build images from the profiles and how to test.

AUTHORS.rst:
Add list of all direct contributors to the repository.

CONTRIBUTING.rst:
Add basic contribution guidelines, explaining the linter and the license in use.

Closes #7
Closes #3

6 files changed, 18 insertions, 0 deletions

diff --git a/configs/releng/airootfs/etc/systemd/system/choose-mirror.service b/configs/releng/airootfs/etc/systemd/system/choose-mirror.service
index b6a3562..b3e4847 100644
--- a/configs/releng/airootfs/etc/systemd/system/choose-mirror.service
+++ b/configs/releng/airootfs/etc/systemd/system/choose-mirror.service
@@ -1,3 +1,6 @@
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+
 [Unit]
 Description=Choose mirror from the kernel command line
 ConditionKernelCommandLine=mirror
diff --git a/configs/releng/airootfs/etc/systemd/system/etc-pacman.d-gnupg.mount b/configs/releng/airootfs/etc/systemd/system/etc-pacman.d-gnupg.mount
index 4eab551..f86a91d 100644
--- a/configs/releng/airootfs/etc/systemd/system/etc-pacman.d-gnupg.mount
+++ b/configs/releng/airootfs/etc/systemd/system/etc-pacman.d-gnupg.mount
@@ -1,3 +1,6 @@
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+
 [Unit]
 Description=Temporary /etc/pacman.d/gnupg directory
 
diff --git a/configs/releng/airootfs/etc/systemd/system/getty@tty1.service.d/autologin.conf b/configs/releng/airootfs/etc/systemd/system/getty@tty1.service.d/autologin.conf
index d1d8474..370735f 100644
--- a/configs/releng/airootfs/etc/systemd/system/getty@tty1.service.d/autologin.conf
+++ b/configs/releng/airootfs/etc/systemd/system/getty@tty1.service.d/autologin.conf
@@ -1,3 +1,6 @@
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+
 [Service]
 ExecStart=
 ExecStart=-/sbin/agetty --autologin root --noclear %I 38400 linux
diff --git a/configs/releng/airootfs/etc/systemd/system/pacman-init.service b/configs/releng/airootfs/etc/systemd/system/pacman-init.service
index 23b8144..3adec4c 100644
--- a/configs/releng/airootfs/etc/systemd/system/pacman-init.service
+++ b/configs/releng/airootfs/etc/systemd/system/pacman-init.service
@@ -1,3 +1,6 @@
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+
 [Unit]
 Description=Initializes Pacman keyring
 Wants=haveged.service
diff --git a/configs/releng/airootfs/etc/systemd/system/reflector.service b/configs/releng/airootfs/etc/systemd/system/reflector.service
index f7a88f2..e15dccf 100644
--- a/configs/releng/airootfs/etc/systemd/system/reflector.service
+++ b/configs/releng/airootfs/etc/systemd/system/reflector.service
@@ -1,3 +1,6 @@
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+
 [Unit]
 Description=pacman mirrorlist update
 Wants=network-online.target
diff --git a/configs/releng/airootfs/etc/systemd/system/systemd-networkd-wait-online.service.d/wait-for-only-one-interface.conf b/configs/releng/airootfs/etc/systemd/system/systemd-networkd-wait-online.service.d/wait-for-only-one-interface.conf
index c875311..1b4c091 100644
--- a/configs/releng/airootfs/etc/systemd/system/systemd-networkd-wait-online.service.d/wait-for-only-one-interface.conf
+++ b/configs/releng/airootfs/etc/systemd/system/systemd-networkd-wait-online.service.d/wait-for-only-one-interface.conf
@@ -1,3 +1,6 @@
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+
 [Service]
 ExecStart=
 ExecStart=/usr/lib/systemd/systemd-networkd-wait-online --any