Fixed some crashes in response strings source generator, reorganized more submodules into their folders

src/NadekoBot/Modules/Nsfw/_Common/Downloaders/Rule34ImageDownloader.cs

@@ -0,0 +1,29 @@
+#nullable disable
+using System.Net.Http.Json;
+
+namespace NadekoBot.Modules.Nsfw.Common;
+
+public class Rule34ImageDownloader : ImageDownloader<Rule34Object>
+{
+    public Rule34ImageDownloader(HttpClient http)
+        : base(Booru.Rule34, http)
+    {
+    }
+
+    public override async Task<List<Rule34Object>> DownloadImagesAsync(
+        string[] tags,
+        int page,
+        bool isExplicit = false,
+        CancellationToken cancel = default)
+    {
+        var tagString = ImageDownloaderHelper.GetTagString(tags);
+        var uri = "https://rule34.xxx/index.php?page=dapi&s=post&q=index&json=1&limit=100"
+                  + $"&tags={tagString}&pid={page}";
+        var images = await _http.GetFromJsonAsync<List<Rule34Object>>(uri, _serializerOptions, cancel);
+
+        if (images is null)
+            return new();
+
+        return images.Where(img => !string.IsNullOrWhiteSpace(img.Image)).ToList();
+    }
+}