Add data directory to .gitignore and include rrdtool dependency in pyproject.toml

.gitignore

@@ -53,6 +53,9 @@ htmlcov/
 config.yaml
 identity.json
 
+# Data
+data/
+
 # Logs
 *.log
 .DS_Store

pyproject.toml

@@ -48,6 +48,10 @@ dependencies = [
 hardware = [
     "pymc_core[hardware]",
 ]
+# RRD metrics (Performance Metrics chart); system librrd required (e.g. apt install rrdtool)
+rrd = [
+    "rrdtool",
+]
 dev = [
     "pytest>=7.4.0",
     "pytest-asyncio>=0.21.0",