Hide checkboxes and icons when no CSS in head is loaded

This seems to help in Firefox's reader mode.
Also adjust images to not be huge without CSS.

Signed-off-by: Danila Fedorin <danila.fedorin@gmail.com>

layouts/shortcodes/sidenote.html

@@ -1,6 +1,6 @@
 <span class="sidenote">
 <label class="sidenote-label" for="{{- .Get 1 -}}">{{- .Get 2 -}}</label>
-<input class="sidenote-checkbox" type="checkbox" id="{{- .Get 1 -}}"></input>
+<input class="sidenote-checkbox" style="display: none;" type="checkbox" id="{{- .Get 1 -}}"></input>
 {{- if $offset := .Get 3 -}}
 <span class="sidenote-content sidenote-{{- .Get 0 -}}" style="margin-top: {{- $offset -}}rem">
 {{- else -}}