Add a table of contents

Create a new table_of_contents partial that includes an auto-generated table of contents if the word
count is over 400 and the "toc" page variable has been set true.

layouts/partials/photo_exif_table.html

@@ -49,7 +49,7 @@
           {{- $focalLength := .Tags.FocalLengthIn35mmFilm | default .Tags.FocalLength -}}
           {{- with $focalLength -}}{{ . }} mm{{- end -}}
         </td>
-        <td class="f-number">{{ with .Tags.FNumber }}ƒ{{ . }}{{ end }}</td>
+        <td class="f-number">{{ with .Tags.FNumber }}{{ printf "ƒ%0.1f" . }}{{ end }}</td>
         <td class="exposure-time">
           {{- with $exposureTime := .Tags.ExposureTime -}}
             {{- if in $exposureTime "/" -}}