docs(templates): update metadata.yml

Author: lowlighter

source/templates/classic/metadata.yml

@@ -1,4 +1,9 @@
 name: "📗 Classic template"
+description: |
+  A template mimicking GitHub visual identity.
+  This is also the default template.
+examples:
+  default: https://github.com/lowlighter/lowlighter/blob/master/metrics.classic.svg
 index: 0
 supports:
   - user

source/templates/markdown/metadata.yml

@@ -1,4 +1,7 @@
 name: "📒 Markdown template"
+description: A template capable of rendering markdown from a given template file.
+examples:
+  default: https://github.com/lowlighter/lowlighter/blob/master/metrics.markdown.png
 index: 3
 supports:
   - user

source/templates/repository/metadata.yml

@@ -1,4 +1,7 @@
 name: "📘 Repository template"
+description: A template mimicking GitHub visual identity and specially crafted for repositories.
+examples:
+  default: https://github.com/lowlighter/lowlighter/blob/master/metrics.repository.svg
 index: 1
 supports:
   - repository

source/templates/terminal/metadata.yml

@@ -1,4 +1,7 @@
 name: "📙 Terminal template"
+description: A template mimicking a SSH session.
+examples:
+  default: https://github.com/lowlighter/lowlighter/blob/master/metrics.terminal.svg
 index: 2
 supports:
   - user