Ports: Add libsixel

This contains `img2sixel`.

Ports/AvailablePorts.md

@@ -75,6 +75,7 @@ Please make sure to keep this list up to date when adding and updating ports. :^
 | [`libphysfs`](libphysfs/)              | PhysicsFS                                                       | 3.0.2                    | https://icculus.org/physfs/                                                    |
 | [`libpng`](libpng/)                    | libpng                                                          | 1.6.37                   | https://libpng.org/                                                            |
 | [`libpuffy`](libpuffy/)                | libpuffy                                                        | 1.0                      | https://github.com/ibara/libpuffy                                              |
+| [`libsixel`](libsixel/)                | libsixel                                                        | 1.8.6                    | https://github.com/saitoha/libsixel                                            |
 | [`libsodium`](libsodium/)              | libsodium                                                       | 1.0.18-stable            | https://doc.libsodium.org/                                                     |
 | [`libtheora`](libtheora/)              | libtheora                                                       | 1.1.1                    | https://www.theora.org/                                                        |
 | [`libtiff`](libtiff/)                  | libtiff                                                         | 4.2.0                    | http://www.libtiff.org/                                                        |

Ports/libsixel/package.sh

@@ -0,0 +1,11 @@
+#!/usr/bin/env -S bash ../.port_include.sh
+port=libsixel
+version=1.8.6
+files="https://github.com/saitoha/libsixel/archive/refs/tags/v${version}.tar.gz ${port}-${version}.tar.gz 37611d60c7dbcee701346967336dbf135fdd5041024d5f650d52fae14c731ab9"
+useconfigure=true
+auth_type=sha256
+configopts="--prefix=${SERENITY_INSTALL_ROOT}/usr/local"
+
+install() {
+    run make install
+}

Ports/libsixel/patches/config.sub.patch

@@ -0,0 +1,13 @@
+diff --git a/config.sub b/config.sub
+index 9ccf09a..3f638ab 100755
+--- a/config.sub
++++ b/config.sub
+@@ -1390,7 +1390,7 @@ case $os in
+ 	      | -powermax* | -dnix* | -nx6 | -nx7 | -sei* | -dragonfly* \
+ 	      | -skyos* | -haiku* | -rdos* | -toppers* | -drops* | -es* \
+ 	      | -onefs* | -tirtos* | -phoenix* | -fuchsia* | -redox* | -bme* \
+-	      | -midnightbsd*)
++	      | -midnightbsd* | -serenity*)
+ 	# Remember, each alternative MUST END IN *, to match a version number.
+ 		;;
+ 	-qnx*)