SafeRe is vulnerable to ReDoS

### Step 1: Please describe your environment

* ZeroNet version: 0.7.2 (4555)

### Step 2: Describe the problem:

["To avoid the ReDoS algorithmic complexity attack" ](https://zeronet.io/docs/site_development/content_json/#regular-expression-limitations) the function bellow is used to validate user defined regular expressions.

https://github.com/HelloZeroNet/ZeroNet/blob/454c0b2e7e000fda7000cba49027541fbf327b96/src/util/SafeRe.py#L10-L22

This function fails to identify regular expressions that can require exponential time complexity to match user inputs.

#### Steps to reproduce:

```
>>> from SafeRe import isSafePattern, match
>>> p = "a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a?aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
>>> isSafePattern(p)
True
>>> match(p, "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa")
```

#### Observed Results:
`match` hangs and the execution never completes.

#### Expected Results:
`isSafePattern` should properly detect that the pattern is unsafe.
Alternatively, `match` should use an algorithm with guaranteed linear time complexity to compile and match inputs (e.g. Thompson NFA).