Add support for Carthage installation

Motivation:

While SPM is the preferred method for pulling in Swift-only libraries, it's support and capabilities are still sometimes short compared to other dependency managers such as Carthage.

Modifications:

- Add shared Xcode project scheme and file.
- Add github action to verify Carthage builds fine
- Rename `swift.yml` workflow to `tests.yml` to properly break up different github action workflows

Result:

Developers should now be able to use either SPM or Carthage to install swift-currency

.github/workflows/other_dep_managers.yml

@@ -0,0 +1,13 @@
+name: 3rd Party Dependency Managers
+
+on: [push]
+
+jobs:
+  carthage:
+    runs-on: macos-latest
+    steps:
+    - uses: actions/checkout@v1
+    - name: Check Carthage version
+      run: carthage version
+    - name: Run Carthage build
+      run: carthage build --no-skip-current

.github/workflows/swift.yml → .github/workflows/tests.yml

@@ -3,7 +3,7 @@ name: Package Tests
 on: [push]
 
 jobs:
-  test-macos-latest:
+  macos-latest:
     runs-on: macos-latest
     steps:
     - uses: actions/checkout@v1

.gitignore

@@ -1,6 +1,8 @@
 .DS_Store
 /.build
 /Packages
-/*.xcodeproj
+*.xcworkspace/
 xcuserdata/
 .swiftpm
+
+Carthage/

swift-currency.xcodeproj/CurrencyTests_Info.plist

@@ -0,0 +1,25 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<plist version="1.0">
+<dict>
+  <key>CFBundleDevelopmentRegion</key>
+  <string>en</string>
+  <key>CFBundleExecutable</key>
+  <string>$(EXECUTABLE_NAME)</string>
+  <key>CFBundleIdentifier</key>
+  <string>$(PRODUCT_BUNDLE_IDENTIFIER)</string>
+  <key>CFBundleInfoDictionaryVersion</key>
+  <string>6.0</string>
+  <key>CFBundleName</key>
+  <string>$(PRODUCT_NAME)</string>
+  <key>CFBundlePackageType</key>
+  <string>BNDL</string>
+  <key>CFBundleShortVersionString</key>
+  <string>1.0</string>
+  <key>CFBundleSignature</key>
+  <string>????</string>
+  <key>CFBundleVersion</key>
+  <string>$(CURRENT_PROJECT_VERSION)</string>
+  <key>NSPrincipalClass</key>
+  <string></string>
+</dict>
+</plist>

swift-currency.xcodeproj/Currency_Info.plist

@@ -0,0 +1,25 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<plist version="1.0">
+<dict>
+  <key>CFBundleDevelopmentRegion</key>
+  <string>en</string>
+  <key>CFBundleExecutable</key>
+  <string>$(EXECUTABLE_NAME)</string>
+  <key>CFBundleIdentifier</key>
+  <string>$(PRODUCT_BUNDLE_IDENTIFIER)</string>
+  <key>CFBundleInfoDictionaryVersion</key>
+  <string>6.0</string>
+  <key>CFBundleName</key>
+  <string>$(PRODUCT_NAME)</string>
+  <key>CFBundlePackageType</key>
+  <string>FMWK</string>
+  <key>CFBundleShortVersionString</key>
+  <string>1.0</string>
+  <key>CFBundleSignature</key>
+  <string>????</string>
+  <key>CFBundleVersion</key>
+  <string>$(CURRENT_PROJECT_VERSION)</string>
+  <key>NSPrincipalClass</key>
+  <string></string>
+</dict>
+</plist>