Adds iOS privacy manifest.

[mvanbeusekom]

Adds the required privacy manifest to the iOS implementation.

Because the geocoding_ios package doesn't collect any privacy data, the privacy manifest can be empty.

Note that we are following the standard Flutter / Cocoapods implementation which has the following caveat:

The large caveat is that we do not currently know if this actually works. This is the method of inclusion that seems to be the consensus among people using Cocoapods, as bundling it directly as a resource causes problems for clients who do not use use_frameworks. (In theory it seems like a manifest would not actually be required in that case since there is no framework, but it has the potential to actually stomp top-level resources.) Hopefully the automated analysis that Apple will eventually roll out will tolerate the file being bundled in a resource bundle in the framework rather than a top-level manifest file. If not, however, it's not clear how Cocoapods can be supported, so we can adopt this common approach for now under the assumption that eventually tooling will adapt to the reality of the ecosystem, and revisit the exact bundling later if necessary.

Source: flutter/packages@c5349bc

Solves #207

Pre-launch Checklist

• I made sure the project builds.
• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I updated pubspec.yaml with an appropriate new version according to the pub versioning philosophy, or this PR is does not need version changes.
• I updated CHANGELOG.md to add a description of the change.
• I updated/added relevant documentation (doc comments with ///).
• I rebased onto main.
• I added new tests to check the change I am making, or this PR does not need tests.
• I made sure all existing and new tests are passing.
• I ran dart format . and committed any changes.
• I ran flutter analyze and fixed any errors.