docs: switch to markdown extension for tip

as per https://github.com/orgs/community/discussions/16925

Author: swiing

README.md

@@ -12,7 +12,8 @@
 
 A bit array object exhibiting the interface of standard ecmascript [TypedArray](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray)'s.
 
-> :bulb: If you are looking for easily applying bitwise operations, check out [@bitarray/es6](https://github.com/swiing/BitArray), which builds on top of the present library. Here, we purposely stick to methods and properties described by the ecmascript specification (there are no bitwise operations on arrays specified by ecmascript).
+> [!TIP]
+> If you are looking for easily applying bitwise operations, check out [@bitarray/es6](https://github.com/swiing/BitArray), which builds on top of the present library. Here, we purposely stick to methods and properties described by the ecmascript specification (there are no bitwise operations on arrays specified by ecmascript).
 
 ## Rationale