fix(lazyimg): normalize config dict in partial instead of shortcode

- move normalization of provided config dictionary keys to lower case
from shortcode to partial
- allows using any case when supplying config dict from other layouts

layouts/shortcodes/lazyimg.html

@@ -1,10 +1,5 @@
 {{ if .IsNamedParams -}}
-    {{ $params := dict }}
-    {{/* Normalize by transforming all keys to lower-case: */}}
-    {{ range $k, $v := .Params -}}
-        {{ $params = $params | merge (dict (lower $k) $v) }}
-    {{- end -}}
-    {{ partial "lazyimg" $params }}
+    {{ partial "lazyimg" .Params }}
 {{- else -}}
     {{ partial "lazyimg" (.Get 0) }}
 {{- end }}