Add hashtag to facebook and hastags to twitter

Hashtag and hastags are the most commonly used features on facebook and
twitter respectively. Adding support to those two will make the library
even more powerful.

This PR add two optional attribute `data-hashtag` for facebook and
`data-hashtags` for twitter.

`data-hashtag` is a single key word without `#` while `data-hashtags`
are comma seperated strings without `#`.

src/shareon.js

@@ -17,7 +17,7 @@ import "./shareon.css";
  * }) => string}}
  */
 const urlBuilderMap = {
-  facebook: (d) => `https://www.facebook.com/sharer/sharer.php?u=${d.url}`,
+  facebook: (d) => `https://www.facebook.com/sharer/sharer.php?u=${d.url}${d.hashtag? `&hashtag=#${d.hashtag}` : ''}`,
   linkedin: (d) => `https://www.linkedin.com/sharing/share-offsite/?url=${d.url}`,
   mastodon: (d) => `https://toot.kytta.dev/?text=${d.title}%0D%0A${d.url}${d.text ? `%0D%0A%0D%0A${d.text}` : ''}${d.via ? `%0D%0A%0D%0A${d.via}` : ''}`,
   messenger: (d) => `https://www.facebook.com/dialog/send?app_id=${d.fbAppId}&link=${d.url}&redirect_uri=${d.url}`,
@@ -26,7 +26,7 @@ const urlBuilderMap = {
   pocket: (d) => `https://getpocket.com/edit.php?url=${d.url}`,
   reddit: (d) => `https://www.reddit.com/submit?title=${d.title}&url=${d.url}`,
   telegram: (d) => `https://telegram.me/share/url?url=${d.url}${d.text ? `&text=${d.text}` : ''}`,
-  twitter: (d) => `https://twitter.com/intent/tweet?url=${d.url}&text=${d.title}${d.via ? `&via=${d.via}` : ''}`,
+  twitter: (d) => `https://twitter.com/intent/tweet?url=${d.url}&text=${d.title}${d.via ? `&via=${d.via}` : ''}${d.hashtags? `&hashtags=${d.hashtags}` : ''}`,
   viber: (d) => `viber://forward?text=${d.title}%0D%0A${d.url}${d.text ? `%0D%0A%0D%0A${d.text}` : ''}`,
   vkontakte: (d) => `https://vk.com/share.php?url=${d.url}&title=${d.title}${d.media ? `&image=${d.media}` : ''}`,
   whatsapp: (d) => `https://wa.me/?text=${d.title}%0D%0A${d.url}${d.text ? `%0D%0A%0D%0A${d.text}` : ''}`,
@@ -85,6 +85,12 @@ const init = () => {
               via: encodeURIComponent(
                 child.dataset.via || container.dataset.via || ""
               ),
+              hashtag: encodeURIComponent(
+                child.dataset.hashtag || container.dataset.hashtag || ""
+              ),
+              hashtags: encodeURIComponent(
+                child.dataset.hashtags?.replaceAll(', ', ',') || container.dataset.hashtags?.replaceAll(', ', ',') || ""
+              ),
               fbAppId: encodeURIComponent(
                 child.dataset.fbAppId || container.dataset.fbAppId || ""
               ),