docs: Update instructions for running developer scripts (apple#80)

### Motivation

The documentation has an example of running one of the developer scripts in the `scripts/` directory. The scripts are not executable, so need explicitly running with `bash`.

### Modifications

Update docs to reflect the need to run the scripts with `bash`.

Relax minimum macOS requirement to 10.15 (apple#63)

### Motivation

Reduce deployment target by 3 versions to gain more adoption.

### Modifications

- Reduced deployment targets by 3 versions
- Modified `client.Package.x` and `server.Package.x` files to reflect
new deployment targets
- Modified documentation to reflect new deployment targets

### Result

Deployment target will be reduced by 3 versions and documentation will
reflect such changes.

### Resolves

- Resolves apple#62

### Related PRs

- Paired with apple/swift-openapi-runtime#18

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Co-authored-by: andrewelliott <>

[Releases] Add a release config (apple#53)

[Releases] Add a release config

### Motivation

Make making releases easier and more standardized.

### Modifications

Like apple/swift-openapi-runtime#14, but for the generator repo.

Adds the config file, which is then used by GitHub when drafting release notes.

### Result

Our next release notes will be drafted automitically, saving us time.

### Test Plan

Already did this for runtime: https://github.com/apple/swift-openapi-runtime/releases/tag/0.1.1


Reviewed by: simonjbeaumont

Builds:
     ✔︎ pull request validation (5.8) - Build finished. 
     ✔︎ pull request validation (5.9) - Build finished. 
     ✔︎ pull request validation (nightly) - Build finished. 
     ✔︎ pull request validation (soundness) - Build finished. 

apple#53

package: Bump swift-format and swift-syntax to 508.0.1 (apple#4)

### Motivation

Our swift-format dependency (508.0.0) had an `.upToNextMinor` version
dependency on swift-argument-parser, which presented challenges for
adopters of swift-openapi-generator who wanted to also use newer
versions of swift-argument-parser. There's just been a release of
swift-format (and swift-syntax) that relaxes its dependency on
swift-argument-parser to an `.upToNextMajor`.

### Modifications

- Bump swift-format and swift-syntax to 508.0.1.

### Result

Adopters will be able to use newer versions of swift-argument-parser
when using swift-openapi-generator.

### Test Plan

CI.

Signed-off-by: Si Beaumont <beaumont@apple.com>