ARM64 Compatibility Issue on macOS (M2 Chip): b64encode Undefined

## Description
I encountered a build error while using the github.com/cloudwego/base64x library on my macOS device with an M2 chip. The error indicates that b64encode is undefined in the base64x.go file.

## Error Details
`../../../../../pkg/mod/github.com/cloudwego/base64x@v0.1.4/base64x.go:90:5: undefined: b64encode`

## Environment
* OS: macOS Ventura (M2 Chip)
* Go Version: go version go1.x.x darwin/arm64
* Library Version: v0.1.4

## Steps to Reproduce
1. Create a simple Go project that uses the github.com/cloudwego/base64x package.
2. Build or run the project on a Mac with an M2 chip (ARM64 architecture).
3. Observe the error.

## Expected Behavior
The library should support ARM64 architecture or provide a fallback mechanism.

## Actual Behavior
The `b64encode` function is undefined, which suggests the library might not support ARM64 architecture.

## Request
Could you confirm if ARM64 architecture is supported by this library? If not, is there a workaround or planned support for ARM64 devices like M1/M2 chips?