Adds shell script to report package code coverage

coverage.sh

@@ -0,0 +1,19 @@
+#!/bin/sh
+
+BIN_PATH="$(swift build --show-bin-path)"
+XCTEST_PATH="$(find ${BIN_PATH} -name '*.xctest')"
+
+COV_BIN=$XCTEST_PATH
+if [[ "$OSTYPE" == "darwin"* ]]; then
+    f="$(basename $XCTEST_PATH .xctest)"
+    COV_BIN="${COV_BIN}/Contents/MacOS/$f"
+fi
+
+swift package clean
+swift test --enable-code-coverage
+
+llvm-cov report \
+    "${COV_BIN}" \
+    -instr-profile=.build/debug/codecov/default.profdata \
+    -ignore-filename-regex=".build|Tests" \
+    -use-color