Add Salary Range support & add to Google Schema

### Is your feature request related to a problem? Please describe
As i saw on #2263 the salary schema was added. For now it only supports one salary amount but no range.
This was added in the PR as further enhancement but no task was created or followed up as far as i see, right @onubrooks?

### Describe the solution you'd like
Ranges should also be supported asap. I would suppose the following. For all current installations we use the _job_salary Field same as it is right now. It will generate a schema like this:

```
"baseSalary": {
"@type": "MonetaryAmount",
"currency": "USD",
"value": {
"@type": "QuantitativeValue",
"value": 40.00,
"unitText": "HOUR"
}
}
```

Additionally we'll add a second field for _job_salary_max. if this field is also filled out we'll generate schema like this:

```
"baseSalary": {
"@type": "MonetaryAmount",
"currency": "USD",
"value": {
"@type": "QuantitativeValue",
"minValue": 40.00,
"maxValue": 50.00,
"unitText": "HOUR"
}
}
```

It respects the Structure of google requested here: https://developers.google.com/search/docs/appearance/structured-data/job-posting

### Describe alternatives you've considered
-

Start by reviewing the salary schema implementation from issue #2263 and trace how the existing _job_salary field is converted into JobPosting structured data. Compare the current single-value output with the Google Job Posting requirements and verify that adding _job_salary_max produces the requested minValue and maxValue output without changing existing installations.

Written by the indexing model from the issue text.