Add Katex in markdown

    Use $$2+2$$

Gemfile

@@ -34,3 +34,5 @@ gem 'jekyll-category-pages', group: :jekyll_plugins
 gem 'jekyll-minifier', group: :jekyll_plugins
 
 gem "sassc", "< 2.2.0"
+
+gem "kramdown-math-katex"

Gemfile.lock

@@ -56,7 +56,12 @@ GEM
     json (2.2.0)
     json-minify (0.0.3)
       json (> 0)
+    katex (0.8.0)
+      execjs (~> 2.7)
     kramdown (2.1.0)
+    kramdown-math-katex (1.0.1)
+      katex (~> 0.4)
+      kramdown (~> 2.0)
     kramdown-parser-gfm (1.1.0)
       kramdown (~> 2.0)
     liquid (4.0.3)
@@ -102,6 +107,7 @@ DEPENDENCIES
   jekyll-katex
   jekyll-minifier
   jekyll-paginate
+  kramdown-math-katex
   minima (~> 2.5)
   sassc (< 2.2.0)
   tzinfo (~> 1.2)

_config.yml

@@ -37,6 +37,9 @@ jekyll-minifier:
         uglifier_args:
                 harmony: true
 
+markdown: kramdown
+kramdown:
+  math_engine: katex
 
 exclude: ['download',_jobs/skeleton.md, README.md]
 include: ['html','download.html']