Zig port of FileHandler

- io directly with iff.zig and filehandler.zig
- Added OpenGL ubuntu build step and made sure lint doesn't start until build is done
- Rewrote motivation section in README

.github/workflows/build.yml

@@ -12,7 +12,7 @@ jobs:
     continue-on-error: true
     strategy:
       matrix:
-        os: [ubuntu-latest, macos-latest, windows-latest]
+        os: [macos-latest, windows-latest]
     runs-on: ${{matrix.os}}
     steps:
       - uses: actions/checkout@v2
@@ -21,7 +21,21 @@ jobs:
         run: zig build
       - name: Test
         run: zig build test
+  ubuntu-build:
+    timeout-minutes: 15
+    continue-on-error: true
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: goto-bus-stop/setup-zig@v2
+      - name: Install OpenGL
+        run: apt-get libglu1-mesa-dev freeglut3-dev mesa-common-dev
+      - name: Build
+        run: zig build
+      - name: Test
+        run: zig build test
   lint:
+    needs: build
     timeout-minutes: 15
     continue-on-error: true
     runs-on: ubuntu-latest