feat: add raw func and allow using funcs in output name

examples/hledger_monthly.md

@@ -0,0 +1,45 @@
+---
+output: "monthly_report_{{.b}}.md"
+params:
+  b:
+    required: true
+    default: 2011-01
+    usage: |
+      Required.
+      The begin time of report.
+      Examples:
+        2025
+        2025-07
+        2025-07-15
+        Jul
+  e:
+    required: true
+    default: 2011-02
+    usage: |
+      Required.
+      The end time of report.
+      Same format as -b
+  f:
+    default: examples/ledger.j
+    usage: The ledger file to parse
+---
+
+# Finance Report from {{.b}} to {{.e}}
+
+## Previous status:
+
+{{ shell "hledger -f $f balancesheet -e $b" }}
+
+## Expenses:
+
+### Expense Summary by Category
+
+{{ shell "hledger -f $f bal expenses -b $b -e $e --depth 3 --sort amount --budget" }}
+
+## Net Income:
+
+{{shell "hledger -f $f income -b $b -e $e --monthly"}}
+
+## Ending balance:
+
+{{shell "hledger -f $f balancesheet -e $e"}}