added ld+json file for google dataset search

README.md

+<!-- Google Dataset Search Metadata -->
+<script type="application/ld+json">
+{
+  "@context": "https://schema.org/",
+  "@type": "Dataset",
+  "name": "Sample ARC",
+  "description": "This dataset contains a sample ARC for testing purposes.",
+  "url": "https://git.nfdi4plants.org/marcel/test-template",
+  "keywords": ["data analysis", "sample data", "metrics", "test data"],
+  "creator": {
+    "@type": "Organization",
+    "name": "Universität Freiburg"
+  },
+  "license": "https://opensource.org/licenses/MIT",
+  "datePublished": "2024-08-26",
+  "distribution": {
+    "@type": "DataDownload",
+    "contentUrl": "https://git.nfdi4plants.org/marcel/test-template/-/blob/a4e7435a307c04cda85ce5bd952547eedfcc606a/isa.investigation.xlsx",
+    "encodingFormat": "application/xlsx"
+  },
+  "spatialCoverage": {
+    "@type": "Place",
+    "name": "Worldwide"
+  },
+  "temporalCoverage": "2024-08-26/2024-08-26",
+  "variableMeasured": ["temperature"]
+}
+</script>
+
+# Sample Dataset Repository
+
+This repository contains a sample dataset for use in data analysis exercises. The data includes measurements for temperature, humidity, and precipitation collected over a one-year period...
+
+[Download Dataset](https://git.nfdi4plants.org/marcel/test-template/-/blob/a4e7435a307c04cda85ce5bd952547eedfcc606a/isa.investigation.xlsx)
+
+
+
 # ARCs
 
 for details, see <https://github.com/nfdi4plants/ARC-specification>