build fails with "Error: no implicit conversion of String into Integer" but --dry-run flag says "Indexing Complete" instead

**EDIT** I've found the cause/solution to the bug I initially reported, so am adjusting this to a feature request:

## I want to suggest a feature:

**Settings should be validated before attempting to push data** and meaningful feedback provided to allow someone to adjust bad config.

### What is your use case for such a feature?

The original issue is fully outlined below. To summarize: a setting in the config was in the wrong format (a number was wrapped in quotes so was treated as a string instead of the number expected by code), however the error was a generic conversion error, which made troubleshooting difficult.

In case someone else encounters this issue, I'm leaving the "bug details" below.

# Original "bug report" below

## I want to report a bug:

`--dry-run` flag gives the "Indexing Complete" status but actual build fails with error: `Error: no implicit conversion of String into Integer`

### What is the current behavior?

Aftger running the command `bundle exec jekyll algolia` I get the following output:

```
Configuration file: E:/Documentation/jekyll-deployment-scripts/jekyll-layout/_config.yml
Processing site...

Progress: |====================================================================|

Progress: |====================================================================|
Settings are already up to date.
Getting list of existing records
Updating records in index stg_help...
Records to delete: 655
Records to add: 1406
jekyll 3.7.4 | Error: no implicit conversion of String into Integer
```

To troubleshoot, I used the `--dry-run` flag (`bundle exec jekyll algolia --dry-run`) which displays "Indexing complete"

```
Configuration file: E:/Documentation/jekyll-deployment-scripts/jekyll-layout/_config.yml
Processing site...

Progress: |====================================================================|

Progress: |====================================================================|
Settings are already up to date.
Getting list of existing records
Updating records in index stg_help...
Records to delete: 655
Records to add: 1406
✔ Indexing complete
```

To troubleshoot further I used the solution mentioned here: https://github.com/algolia/jekyll-algolia/issues/22#issuecomment-353566802

Using the json data file generated by the plugin linked above, I was successfully able to manually upload the whole data set in one go - I assumed that something about the data was off but there were no error messages when I submitted via the "manual upload" option on the web.

At this point, the value of the plugin (auto-updating the right records) is lost to me until I can figure out what setting, frontmatter, or other thing is causing the issue. Is there something I should look for in the content? (e.g. if my frontmatter has numeric properties, is that causing the issue?).

### What is your expected behavior?
I expect either:
1) the `--dry-run` option should produce similar results to the live build.
2) a meaningful error message pointing to what data, line of json, or file caused the failure to upload.

### Ruby version used:
This issue is consistent on two different platforms building the same content/config files (one's a build server - linux, one's my desktop - windows 10). Here are both ruby versions

windows: ruby 2.6.6p146 (2020-03-31 revision 67876) [x64-mingw32]

linux: ruby 2.5.1p57 (2018-03-29 revision 63029 [x86_64-linux-gnu]

### Jekyll version used:

windows: jekyll 3.7.4

linux: jekyll 3.8.5

## Cause/Resolution

The issue was due to the setting `indexing_batch_size` in quotes in _config.yml

Broken:
```yaml
algolia:
application_id: "XKCD797" # from account
search_only_api_key: "00000000000000000000000000000000" # from account
index_name: "my_index" # from account
indexing_batch_size: "500" #BROKEN LINE IS HERE
nodes_to_index: 'p,li,blockquote,dd'
files_to_exclude: []
```

Working:
```yml
algolia:
application_id: "XKCD797" # from account
search_only_api_key: "00000000000000000000000000000000" # from account
index_name: "my_index" # from account
indexing_batch_size: 500 #FIXED LINE IS HERE
nodes_to_index: 'p,li,blockquote,dd'
files_to_exclude: []
```

Start with the `bundle exec jekyll algolia` entry point and the `algolia` settings shown in `_config.yml`, especially `indexing_batch_size`; compare live and `--dry-run` behavior. Done means invalid setting types are detected before pushing data and produce meaningful feedback identifying the problematic configuration.

Written by the indexing model from the issue text.