Update variables names to camelCase format for consistency (#473)

Clément Pannetier

04.28.2020 c5fbd48e918a6f43281ee4bb81c9b25922fe7758

 layouts/posts/single.html

@@ -28,8 +28,8 @@
      </header>

      <div>
        {{ if .Params.featured_image }}
          <img src='{{ .Params.featured_image }}' alt="Featured image"/>
        {{ if .Params.featuredImage }}
          <img src='{{ .Params.featuredImage }}' alt="Featured image"/>
        {{ end }}
        {{ .Content }}
      </div>