Add markdown format support (#25)

Co-authored-by: Dawid Dziurla <dawidd0811@gmail.com>

node_modules/showdown/.appveyor.yml

@@ -0,0 +1,40 @@
+# branches to build
+#branches:
+  # whitelist
+  #only:
+  #  - master
+
+# What combinations to test
+environment:
+  matrix:
+    - nodejs_version: "6"
+      platform: x64
+    - nodejs_version: "6"
+      platform: x86
+    - nodejs_version: "8"
+      platform: x86
+    - nodejs_version: "8"
+      platform: x64
+    - nodejs_version: "10"
+      platform: x64
+
+install:
+  # Use version based on tag
+  - ps: $env:package_version = (Get-Content -Raw -Path package.json | ConvertFrom-Json).version
+  - ps: Update-AppveyorBuild -Version "$env:package_version-$env:APPVEYOR_BUILD_NUMBER"
+
+  # install node
+  # Get the latest stable version of Node.js or io.js
+  - ps: Install-Product node $env:nodejs_version
+  # install grunt-cli globally
+  - npm install -g grunt-cli
+  # install modules
+  - npm install
+
+test_script:
+  # Output useful info for debugging
+  - node --version && npm --version
+  - ps: grunt test
+
+# Don't actually build.
+build: off