(feat) Update dotfile scripts & tooling

- Update & split scripts
- Main package install script
- Fish / environment install script
- Dockerfile for testing locally

fish/theme-t31m/functions/envsource.fish

@@ -0,0 +1,12 @@
+# Place this in your Fish functions folder to make it available immediately
+# e.g. ~/.config/fish/functions/envsource.fish
+#
+# Usage: envsource <path/to/env>
+
+function envsource
+  for line in (cat $argv | grep -v '^#')
+    set item (string split -m 1 '=' $line)
+    set -gx $item[1] $item[2]
+    echo "Exported key $item[1]"
+  end
+end