Update matrixbuild to current Linux distributions (#55)

Previously, at the time of #50, broken Fedora Rawhide, 35, CentOS
Stream 9 (development) have been fixed. Switch Alpine 3.14 -> 3.15.

.github/images/centos.Dockerfile

@@ -3,7 +3,7 @@ FROM quay.io/$image
 
 # Install dependencies
 RUN yum update -y
-RUN yum install -y autoconf automake gcc libtool make
+RUN yum install -y autoconf automake gcc libtool make diffutils file
 
 # Add source code
 ADD . /src

.github/images/fedora/fedora:35.Dockerfile

@@ -0,0 +1 @@
+../centos.Dockerfile

.github/images/fedora/fedora:36.Dockerfile

@@ -0,0 +1 @@
+../centos.Dockerfile

.github/workflows/matrixbuild.yml

@@ -14,13 +14,15 @@ jobs:
           - debian:buster
           - ubuntu:focal
           - ubuntu:bionic
+          - fedora/fedora:36
+          - fedora/fedora:35
           - fedora/fedora:34
-          - fedora/fedora:33
+          - centos/centos:stream9
           - centos/centos:stream8
           - centos/centos:7
           - rockylinux/rockylinux:8
           - alpine:edge
-          - alpine:3.14
+          - alpine:3.15
     steps:
     - uses: actions/checkout@v1
     - name: Run build on ${{matrix.dockerenv}}