String + Format parse fails when string includes 'dddd'

**Describe the bug**
Using the version on the dayjs website (via the web console), I can construct dates like `Tuesday Feb 1/22 ` with

```
date = dayjs(new Date())
date.format('dddd MMM D/YY')
```

But attempting to parse them with the same format string returns `Invalid Date`

```
dayjs('Tuesday Feb 1/22', 'dddd MMM D/YY')
```

**Expected behavior**

the parser would return a valid dayjs object

**Information**
- Day.js Version [e.g. v1.0.0]
on the dayjs docs website
- OS: [e.g. iOS]
mac
- Browser [e.g. chrome 62]
safari 15.2
- Time zone: [e.g. GMT-07:00 DST (Pacific Daylight Time)]

Start by reproducing the documented format and parse calls in the Day.js web console, then trace the parsing path used for the `dddd MMM D/YY` format. Done means parsing `Tuesday Feb 1/22` returns a valid Day.js object instead of `Invalid Date`.

Written by the indexing model from the issue text.