Indentation in "add_CH3" command 

In "add_CH3", the arguments are the same indentation level, so change it to one indentation level.

before:
```
add_CH3: true
root: /model_1/A/30/461_SG
displacement: /model_1/A/201/1605_CAB
```

after:
```
add_CH3:
  root: /model_1/A/30/461_SG
  displacement: /model_1/A/201/1605_CAB
```
