Format Markdown files with YAML metadata.

Add the mdformat packages to the pre-commit hook needed for that. Format
the existing files.

.pre-commit-config.yaml

@@ -51,7 +51,9 @@ repos:
     rev: 0.7.10
     hooks:
       - id: mdformat
-        exclude: example
+        additional_dependencies:
+          - mdformat-frontmatter
+          - mdformat-gfm
 
   - repo: https://git.shore.co.il/nimrod/pre-commit-hooks.git
     rev: v0.2.0

example/left-to-right.md

@@ -2,8 +2,7 @@
 dir: rtl
 lang: he
 mainfont: SILEOT.ttf
-...
-
+---
 
 # משהו בעברית
 

example/presentation.md

@@ -2,7 +2,7 @@
 title: Presentation
 author: Your name here
 theme: metropolis
-...
+---
 
 # Section
 
@@ -20,4 +20,5 @@ theme: metropolis
 ![Animated gif](prompt.gif)
 
 ## External image
+
 ![External image](https://git.shore.co.il/nimrod/rcfiles/-/raw/master/.face)