Add option to show link in meta data for editing posts (#278)

Usage

- in site config =>

    Params:
    editPost:
        URL: "https://github.com/<path_to_repo>/content"
        Text: "Suggest Changes" # edit text 
        appendFilePath: true # to append file path to Edit link

- in front-matter vars =>
    ---
    editPost:
        URL: "https://github.com/<path_to_repo>/content"
        Text: "Suggest Changes" # edit text 
        appendFilePath: true # to append file path to Edit link
    ---

- Front-matter vars overrides global ones

i18n/de.yaml

@@ -14,3 +14,6 @@
 
 - id: translations
   translation: "Übersetzungen"
+
+- id: edit_post
+  translation: "Bearbeiten"

layouts/_default/single.html

@@ -16,6 +16,7 @@
     <div class="post-meta">
       {{- partial "post_meta.html" .  -}}
       {{- partial "translation_list.html" . -}}
+      {{- partial "edit_post.html" . -}}
     </div>
     {{- end}}
   </header>

layouts/partials/edit_post.html

@@ -0,0 +1,6 @@
+{{- if or .Params.editPost.URL .Site.Params.editPost.URL -}}
+{{- if or .Params.author $.Site.Params.author (.Param "ShowReadingTime") (not .Date.IsZero) .IsTranslated }}| {{- end -}}
+<a href="{{ .Params.editPost.URL | default .Site.Params.editPost.URL }}{{ if .Params.editPost.appendFilePath | default ( .Site.Params.editPost.appendFilePath | default false ) }}/{{ .File.Path }}{{ end }}" rel="noopener noreferrer" target="_blank">
+    {{- .Params.editPost.Text | default (.Site.Params.editPost.Text | default (i18n "edit_post" | default "Edit") ) -}}
+</a>
+{{- end }}