Add a mechanism for building a cache of "system parameters"

- Add a system_parameters module to eryntools that implements some basic types and can write a cache to a file.
- Add a system-parameters Python script that builds the cache.
- Add init_system_parameters to zsh that exports an environment variable that points to the parameters file
- Add an eryn.system-parameters.plist LaunchAgent file for running the script at regular intervals

LaunchAgents/eryn.system-parameters.plist

@@ -0,0 +1,27 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+  <dict>
+    <key>Label</key>
+    <string>eryn.system-parameters</string>
+    <key>ProgramArguments</key>
+    <array>
+        <string>/Users/eryn/bin/system-parameters</string>
+        <string>--output</string>
+        <string>/Users/eryn/.config/eryn/system_parameters.json</string>
+    </array>
+    <key>WorkingDirectory</key>
+    <string>/Users/eryn</string>
+    <key>StandardOutPath</key>
+    <string>/Users/eryn/.config/eryn/system_parameters.output.log</string>
+    <key>StandardErrorPath</key>
+    <string>/Users/eryn/.config/eryn/system_parameters.error.log</string>
+    <key>EnvironmentVariables</key>
+    <dict>
+      <key>PATH</key>
+      <string>/opt/homebrew/bin:/usr/local/bin:/usr/bin:/bin</string>
+    </dict>
+    <key>RunAtLoad</key>
+    <true/>
+  </dict>
+</plist>