fix: run libsodium on WebAssembly under the extension CSP (closes #182)

manifest/chrome.json

@@ -5,6 +5,9 @@
     "description": "Minimal Ethereum wallet for Chrome",
     "permissions": ["storage", "activeTab", "alarms"],
     "host_permissions": ["<all_urls>"],
+    "content_security_policy": {
+        "extension_pages": "script-src 'self' 'wasm-unsafe-eval'; object-src 'self'"
+    },
     "action": {
         "default_popup": "src/popup/index.html"
     },

manifest/firefox.json

@@ -4,6 +4,7 @@
     "version": "0.1.0",
     "description": "Minimal Ethereum wallet for Firefox",
     "permissions": ["storage", "activeTab", "alarms", "<all_urls>"],
+    "content_security_policy": "script-src 'self' 'wasm-unsafe-eval'; object-src 'self'",
     "browser_action": {
         "default_popup": "src/popup/index.html"
     },