defaultValidators.js node regex matches everything

[avinxshKD]

var regex = /^[A-za-z0-9]+[:[A-Za-z0-9.]+]|[^$]$/;

this has three issues:

1. A-z includes []^_` (should be A-Z)
2. [:[A-Za-z0-9.]+] is a character class not a group
3. |[^$]$ matches any string ending in non-$ char, so basically everything

Creating a node with label !!! or <script>, passes fine

Should probably be /^[A-Za-z0-9]+(:[A-Za-z0-9.]+)?$/ but honestly depends on what the actual label format is supposed to be. Current regex validates nothin

[avinxshKD]

very small fix, raising a pr thanks