Set `main` attribute in `package.json`

Don't set `strophe.js` as dependency twice.

package-lock.json

@@ -27,7 +27,6 @@
         "pluggable.js": "^3.0.1",
         "sizzle": "^2.3.5",
         "sprintf-js": "^1.1.2",
-        "strophe.js": "^1.6.2",
         "urijs": "^1.19.10"
       },
       "devDependencies": {

package.json

@@ -2,6 +2,7 @@
   "name": "converse.js",
   "version": "10.1.5",
   "description": "Browser based XMPP chat client",
+  "main": "src/index.js",
   "browser": "dist/converse.js",
   "module": "src/index.js",
   "workspaces": [
@@ -126,7 +127,6 @@
     "pluggable.js": "^3.0.1",
     "sizzle": "^2.3.5",
     "sprintf-js": "^1.1.2",
-    "strophe.js": "^1.6.2",
     "urijs": "^1.19.10"
   },
   "resolutions": {

src/headless/package.json

@@ -8,7 +8,8 @@
   ],
   "homepage": "https://conversejs.org",
   "license": "MPL-2.0",
-  "main": "dist/converse-headless.js",
+  "main": "index.js",
+  "browser": "dist/converse-headless.js",
   "module": "index.js",
   "keywords": [
     "converse.js",