Add Fira font files to project

Because the GitLab CI can’t run apt-get at the moment, the font must be
embedded into the project instead of installed in the container.
Also, a switch is added so that if a machine has the font installed, it
uses that version. This is needed because LuaLaTeX doesn’t like using
the project .ttf files on my machine. So this is a workaround for that.

.gitattributes

@@ -2,3 +2,7 @@ assets/rust-logo-blk.svg filter=lfs diff=lfs merge=lfs -text
 assets/copper_patina.jpg filter=lfs diff=lfs merge=lfs -text
 assets/verdigris-logo.xcf filter=lfs diff=lfs merge=lfs -text
 assets/verdigris-logo.png filter=lfs diff=lfs merge=lfs -text
+fonts/FiraMono-RegularItalic.otf filter=lfs diff=lfs merge=lfs -text
+fonts/FiraCode-Bold.ttf filter=lfs diff=lfs merge=lfs -text
+fonts/FiraCode-Regular.ttf filter=lfs diff=lfs merge=lfs -text
+fonts/FiraMono-BoldItalic.otf filter=lfs diff=lfs merge=lfs -text

preamble.tex

@@ -2,7 +2,18 @@
 % Font and Language
 %%%
 \usepackage{fontspec}
-\setmonofont{Fira Code}[RawFeature={+onum, +ss07}]
+\IfFontExistsTF{Fira Code}{
+    \setmonofont{Fira Code}[RawFeature={+onum, +ss07}]
+}{
+    \setmonofont{FiraCode-Regular.ttf}[%
+        Path = ../fonts/,%
+        BoldFont = ../fonts/FiraCode-Bold.ttf,%
+        % FiraCode has no italics itself, so we borrow from FiraMono:
+        ItalicFont = ../fonts/FiraMono-RegularItalic.otf,%
+        BoldItalicFont = ../fonts/FiraMono-BoldItalic.otf,%
+        RawFeature={+onum, +ss07}
+    ]
+}
 
 \usepackage{polyglossia}
 \setdefaultlanguage{german}