Add Mistyk__@Showdown mod (#464)

Showdown is a content mod that adds a little bit of everything in top of
adding its own things.

mods/Mistyk__@Showdown/description.md

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+**Showdown** is an overall content mod for Balatro. It focuses mostly on new ranks, a new set of cards and fun jokers. It currently adds:
+- 7 Ranks
+- 77 Jokers
+- 6 Decks
+- 4 Vouchers
+- 6 Tarot Cards
+- 2 Spectral Cards
+- 2 new sets of cards:
+- - 8 Mathematic Cards
+- - 10 Logic Cards
+- 2 Enhancements
+- 8 Stickers
+- 27 Tags
+- 24 Blinds
+- 7 Stakes
+- 12 Achievements
+
+The mod is compatible with some other mods, check this out:
+- Card Sleeves:
+  - 6 Sleeves
+- Bunco:
+  - 1 Tarot Card
+
+The mod content is configurable! You can deactivate any category of items or any mod compatibility in the mod config.
+
+You currently need **Steamodded Alpha 1.0.0** version **0827c** at least

mods/Mistyk__@Showdown/meta.json

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+{
+  "title": "Showdown",
+  "requires-steamodded": true,
+  "requires-talisman": false,
+  "categories": [
+    "Content"
+  ],
+  "author": "Mistyk__",
+  "repo": "https://github.com/Mistyk1/Showdown",
+  "downloadURL": "https://github.com/Mistyk1/Showdown/releases/latest/download/Showdown.zip",
+  "folderName": "Showdown",
+  "version": "1.4",
+  "automatic-version-check": true
+}