add option to disable the "Select Media to Download" for embeds (#485)

- Fixes #486 
- Adding `nomediadownload` attr, eg. `<replay-web-page nomediadownload
...>` will hide the new option in the main menu.
- Add a general EmbedOpts that setting that can be used to configure
other embedding options.

src/embed.ts

@@ -66,6 +66,8 @@ class Embed extends LitElement {
   @property({ type: Boolean }) noCache = false;
   @property({ type: Boolean }) hideOffscreen: boolean | undefined;
 
+  @property({ type: Boolean }) noMediaDownload = false;
+
   @property({ type: Boolean }) useAdblock = false;
   @property({ type: String }) adblockRulesUrl = DEFAULT_ADBLOCK_FILE;
 
@@ -324,6 +326,7 @@ class Embed extends LitElement {
         swName?: string;
         ruffle?: "1";
         adblockUrl?: string;
+        noMediaDownload?: string;
       } = {
         source,
         customColl: this.coll,
@@ -365,6 +368,10 @@ class Embed extends LitElement {
         params.adblockUrl = this.adblockRulesUrl;
       }
 
+      if (this.noMediaDownload) {
+        params.noMediaDownload = "1";
+      }
+
       this.paramString = new URLSearchParams(
         // Converting to unknown here so that we can ignore the URL -> string conversion necessary for the types to work out
         params as unknown as Record<string, string>,