Use chroma theme: dracula

Rather than defining all of the colours ourselves, we can simply choose
a theme that is supported by `chroma`.

examples/slides.md

@@ -1,6 +1,16 @@
 # Welcome to Slides
 A terminal based presentation tool
 
+```go
+package main
+
+import "fmt"
+
+func main() {
+  fmt.Println("Written in Go!")
+}
+```
+
 ---
 
 ## Everything is markdown
@@ -15,7 +25,6 @@ In fact this entire presentation is a markdown file
 ##### h5
 ###### h6
 
-
 # Markdown components
 You can use everything in markdown!
 * Like bulleted list
@@ -33,9 +42,11 @@ All you need to do is separate slides with triple dashes `---` on a separate lin
 like so:
 
 ```markdown
-Slide 1
+# Slide 1
+Some stuff
 
 --- 
 
-Slide 2
+# Slide 2
+Some other stuff
 ```

styles/theme.json

@@ -85,96 +85,8 @@
     "background_color": "236"
   },
   "code_block": {
-    "color": "244",
-    "margin": 2,
-    "chroma": {
-      "text": {
-        "color": "#C4C4C4"
-      },
-      "error": {
-        "color": "#F1F1F1",
-        "background_color": "#F05B5B"
-      },
-      "comment": {
-        "color": "#676767"
-      },
-      "comment_preproc": {
-        "color": "#FF875F"
-      },
-      "keyword": {
-        "color": "#00AAFF"
-      },
-      "keyword_reserved": {
-        "color": "#FF5FD2"
-      },
-      "keyword_namespace": {
-        "color": "#FF5F87"
-      },
-      "keyword_type": {
-        "color": "#6E6ED8"
-      },
-      "operator": {
-        "color": "#EF8080"
-      },
-      "punctuation": {
-        "color": "#E8E8A8"
-      },
-      "name": {
-        "color": "#C4C4C4"
-      },
-      "name_builtin": {
-        "color": "#FF8EC7"
-      },
-      "name_tag": {
-        "color": "#B083EA"
-      },
-      "name_attribute": {
-        "color": "#7A7AE6"
-      },
-      "name_class": {
-        "color": "#F1F1F1",
-        "underline": true,
-        "bold": true
-      },
-      "name_constant": {},
-      "name_decorator": {
-        "color": "#FFFF87"
-      },
-      "name_exception": {},
-      "name_function": {
-        "color": "#00D787"
-      },
-      "name_other": {},
-      "literal": {},
-      "literal_number": {
-        "color": "#6EEFC0"
-      },
-      "literal_date": {},
-      "literal_string": {
-        "color": "#C69669"
-      },
-      "literal_string_escape": {
-        "color": "#AFFFD7"
-      },
-      "generic_deleted": {
-        "color": "#FD5B5B"
-      },
-      "generic_emph": {
-        "italic": true
-      },
-      "generic_inserted": {
-        "color": "#00D787"
-      },
-      "generic_strong": {
-        "bold": true
-      },
-      "generic_subheading": {
-        "color": "#777777"
-      },
-      "background": {
-        "background_color": "#373737"
-      }
-    }
+    "theme": "dracula",
+    "margin": 2
   },
   "table": {
     "center_separator": "┼",