Update Package.swift to remove Foundation import (#3)

Prefer using `PackageDescription.Context.environment` instead of
using `ProcessInfo().environment` directly.

Author: Kyle-Ye

Examples/Life/Package.swift

@@ -1,11 +1,10 @@
 // swift-tools-version: 5.9
 
-import Foundation
 import PackageDescription
 
 let gccIncludePrefix =
   "/usr/local/playdate/gcc-arm-none-eabi-9-2019-q4-major/lib/gcc/arm-none-eabi/9.2.1"
-guard let home = ProcessInfo().environment["HOME"] else {
+guard let home = Context.environment["HOME"] else {
   fatalError("could not determine home directory")
 }
 

Examples/SwiftBreak/Package.swift

@@ -1,11 +1,10 @@
 // swift-tools-version: 5.9
 
-import Foundation
 import PackageDescription
 
 let gccIncludePrefix =
   "/usr/local/playdate/gcc-arm-none-eabi-9-2019-q4-major/lib/gcc/arm-none-eabi/9.2.1"
-guard let home = ProcessInfo().environment["HOME"] else {
+guard let home = Context.environment["HOME"] else {
   fatalError("could not determine home directory")
 }
 

Examples/Template/Package.swift

@@ -1,11 +1,10 @@
 // swift-tools-version: 5.9
 
-import Foundation
 import PackageDescription
 
 let gccIncludePrefix =
   "/usr/local/playdate/gcc-arm-none-eabi-9-2019-q4-major/lib/gcc/arm-none-eabi/9.2.1"
-guard let home = ProcessInfo().environment["HOME"] else {
+guard let home = Context.environment["HOME"] else {
   fatalError("could not determine home directory")
 }
 

Package.swift

@@ -1,11 +1,10 @@
 // swift-tools-version: 5.9
 
-import Foundation
 import PackageDescription
 
 let gccIncludePrefix =
   "/usr/local/playdate/gcc-arm-none-eabi-9-2019-q4-major/lib/gcc/arm-none-eabi/9.2.1"
-guard let home = ProcessInfo.processInfo.environment["HOME"] else {
+guard let home = Context.environment["HOME"] else {
   fatalError("could not determine home directory")
 }