Fixed BMPString encoding (#111)

* Fixed #110 by using UTF-16 to encode the string literal
* Added a unit test to test the added functionality

Co-authored-by: Bram Kolkman <[email protected]>

Drop Swift 5.10 (#108)

### Motivation:

Swift 5.10 is no longer supported, we should bump the swift-tools
version.

### Modifications:

* Update Swift tools version to 6.0
* Add `strictConcurrencyDevelopment` mode

### Result:

Code reflects our support window.

Introduced -Xswiftc -Xfrontend flag to GA workflow. (#104)

Introduced -Xswiftc -Xfrontend flag to GA workflow. There were no
Sendability warnings to fix after this change.

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Co-authored-by: George Barnett <[email protected]>

add thresholds for Swift 6.1 from 6.0 thresholds (#101)

- **Enable Swift 6.1 jobs in CI**
- **add thresholds for Swift 6.1 from 6.0 thresholds**

Merge commit from fork

* Throw error instead of halting when the encoding is invalid

Signed-off-by: Cory Benfield <[email protected]>

* Avoid extra precondition failure

---------

Signed-off-by: Cory Benfield <[email protected]>
Co-authored-by: Nicolas Bachschmidt <[email protected]>

Drop Swift 5.8 (#69)

We no longer support Swift 5.8, so let's wave it goodbye

Update swift-syntax link to swiftlang/swift-syntax (#57)

Remove note from README about API instability (#45)

I think we can remove that note now that the library has 1.0.0 tag.

Support multi PEM parsing and speed up PEM parsing in general (#39)

* Multi PEM support

* Multi PEM support

* swift-format

* Apply review feedback

Support multi PEM parsing and speed up PEM parsing in general (#39)

* Multi PEM support

* Multi PEM support

* swift-format

* Apply review feedback