docs: update README

suzuki-shunsuke · Oct 15, 2020 · eb22f82 · eb22f82
1 parent 1a22d69
commit eb22f82
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diff --git a/README.md b/README.md
@@ -364,6 +364,21 @@ ex.
 
 We can test external Tengo scripts with [suzuki-shunsuke/tengo-tester](https://github.com/suzuki-shunsuke/tengo-tester).
 
+## Restriction: map key should be string
+
+* meta
+* phase.meta
+* task.meta
+* task.items
+
+NG
+
+```yaml
+---
+meta:
+  true: foo # invalid key: key should be string
+```
+
 ## Configuration Reference
 
 ```yaml