docs: add example how to use Combine to prepare batches for write into InfluxDB

[bednar]

Closes #43

Proposed Changes

1. Added an example how to use Combine to prepare batches for write into InfluxDB

Checklist

• [x] CHANGELOG.md updated
• [x] Rebased/mergeable
• [x] swift test completes successfully
• [x] Commit messages are in semantic format
• [x] Sign CLA (if not already signed)

[codecov-commenter]

Codecov Report

Merging #44 (6e90ffd) into master (d7e9b67) will increase coverage by 35.58%. The diff coverage is n/a.

@@             Coverage Diff             @@
##           master      #44       +/-   ##
===========================================
+ Coverage   51.68%   87.27%   +35.58%     
===========================================
  Files         137       10      -127     
  Lines        6240      707     -5533     
===========================================
- Hits         3225      617     -2608     
+ Misses       3015       90     -2925     

Impacted Files	Coverage Δ
...wiftApis/Generated/Models/SecretKeysResponse.swift
...es/InfluxDBSwiftApis/Generated/Models/Bucket.swift
Tests/InfluxDBSwiftTests/IntegrationTests.swift
...fluxDBSwiftApis/Generated/Models/HealthCheck.swift
Tests/InfluxDBSwiftApisTests/PingAPITests.swift
...ces/InfluxDBSwiftApis/Generated/Models/DBRPs.swift
...es/InfluxDBSwiftApis/Generated/APIs/ReadyAPI.swift
Tests/InfluxDBSwiftTests/WriteAPITests.swift
...fluxDBSwiftApis/Generated/Models/BucketLinks.swift
...ces/InfluxDBSwiftApis/Generated/Models/Ready.swift
... and 117 more

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