Showcase fixes (#349)

* Fix Dandelion link

* Remove xhibit as it seems broken. (502)

* Remove seeada as it seems it is gone.

* Remove metromermaids as the site can't be reached

* Remove cardanowaves as the site seems to not respond

* Remove cardanoalerts as the site seems to not respond

src/data/builder-tools.js

@@ -115,7 +115,7 @@ const Showcases = [
     description:
       "Kubernetes-based project to easily deploy Cardano APIs and a free, hosted community service to access all of them instantly.",
     preview: require("./builder-tools/dandelion-apis.png"),
-    website: "https://gimbalabs.com/dandelionapis",
+    website: "https://gimbalabs.com/dandelion",
     getstarted: "/docs/get-started/dandelion-apis",
     tags: ["getstarted", "api"],
   },

src/data/showcases.js

@@ -370,15 +370,6 @@ const Showcases = [
     source: null,
     tags: ["pooltool", "analytics", "tokens"],
   },
-  {
-    title: "See Ada",
-    description:
-      "This project tracks the controlled stake of the top pool operators and monitors decentralization.",
-    preview: require("./showcase/seeada.png"),
-    website: "https://seeada.org",
-    source: null,
-    tags: ["analytics"],
-  },
   {
     title: "Cardano Blockchain Insights",
     description:
@@ -389,15 +380,6 @@ const Showcases = [
     source: null,
     tags: ["analytics"],
   },
-  {
-    title: "Xhibit",
-    description:
-      "Create your own NFT or look into recently minted NFTs on Cardano.",
-    preview: require("./showcase/xhibit.png"),
-    website: "https://xhibit.io",
-    source: null,
-    tags: ["tokens", "nft"],
-  },
   {
     title: "Token Tool",
     description: "Keep track of native tokens on testnet and mainnet.",
@@ -639,33 +621,6 @@ const Showcases = [
     source: null,
     tags: ["nft", "game"],
   },
-  {
-    title: "Cardano Waves",
-    description:
-      "The largest collection of real-time charts for the Cardano network and community.",
-    preview: require("./showcase/cardano-waves.png"),
-    website: "https://cardanowaves.com",
-    source: null,
-    tags: ["analytics"],
-  },
-  {
-    title: "Cardano Alerts",
-    description:
-      "Get wallet notifications or keep tabs on your Cardano stake pool with real time alerts.",
-    preview: require("./showcase/cardano-alerts.png"),
-    website: "https://cardanoalerts.com",
-    source: null,
-    tags: ["pooltool"],
-  },
-  {
-    title: "Metro Mermaids NFT Maker",
-    description:
-      "Mint and Burn NFTs",
-    preview: require("./showcase/metromermaids.png"),
-    website: "https://mint.metromermaids.com",
-    source: null,
-    tags: ["tokens", "nft"],
-  },
   {
     title: "Cardano Token and NFT Builder",
     description: