Allow including images from `img` directory

main.tex

@@ -1,6 +1,8 @@
 \documentclass[12pt,titlepage,a4paper,twoside]{article}
     \include{packages}
 
+    \graphicspath{{$inputDir$/img/}}
+
     \renewcommand{\thesection}{}
     \renewcommand{\thesubsection}{\arabic{section}.\arabic{subsection}}
     \makeatletter

packages.tex

@@ -9,6 +9,7 @@
 \usepackage{url}
 \usepackage{ellipsis}
 \usepackage[margin=1in,includefoot]{geometry}
+\usepackage{graphicx}
 
 \hypersetup{
     hidelinks=true

test/main.md

@@ -8,3 +8,6 @@ subtitle: Test Document
 \lipsum[3-15]
 
 Foo is equal to \$foo\$.
+Input directory is at \$inputDir\$.
+
+\includegraphics[width=\textwidth]{test-image}

variables.lua

@@ -2,16 +2,23 @@ local vars = {}
 
 local additionalChars = {".", ",", "!", ":", ";"}
 
-local function getVars(meta)
+
+local function setVariable(meta, key, val)
+    local var_key = "$" .. key .. "$"
+    vars[var_key] = val
+    meta[key] = val
+    for _, char in pairs(additionalChars) do
+        vars[var_key .. char] = val .. char
+        vars[char .. var_key] = char .. val
+        meta[var_key .. char] = val .. char
+        meta[char .. var_key] = char .. val
+    end
+end
+
+local function getVarsFromMeta(meta)
     for k, v in pairs(meta) do
         if v.t == 'MetaInlines' then
-            local var_key = "$" .. k .. "$"
-            local var_value = table.unpack(v)["c"]
-            vars[var_key] = var_value
-            for _, char in pairs(additionalChars) do
-                vars[var_key .. char] = var_value .. char
-                vars[char .. var_key] = char .. var_value
-            end
+            setVariable(meta, k, table.unpack(v)["c"])
         end
     end
     return meta
@@ -20,9 +27,9 @@ end
 return {
     {
         Meta = function (meta)
-            meta = getVars(meta)
-            meta['outputFile'] = os.getenv("OUTPUT_FILE")
-            meta['inputDir'] = os.getenv("INPUT_DIR")
+            setVariable(meta, 'outputFile', os.getenv("OUTPUT_FILE"))
+            setVariable(meta, 'inputDir', os.getenv("INPUT_DIR"))
+            return getVarsFromMeta(meta)
         end
     },
     {