Fix firefox ability to load file, add firefox tests back (#1380)

## Launch Checklist

This PR fixes the problem with firefox not able to load a file when
clicking the open file button.
It does so by removing a very old dependency: `react-file-reader-input`
It uses the "regular" `<label><a/><input type="file" /><label>`
approach.
It adds tests for both firefox and chrome although I'm not sure the
firefox tests will stay...

 - [x] Briefly describe the changes in this PR.
 - [x] Write tests for all new functionality.
 - [x] Add an entry to `CHANGELOG.md` under the `## main` section.

package-lock.json

@@ -51,7 +51,6 @@
         "react-collapse": "^5.1.1",
         "react-color": "^2.19.3",
         "react-dom": "^19.1.1",
-        "react-file-reader-input": "^2.0.0",
         "react-i18next": "^15.7.3",
         "react-icons": "^5.5.0",
         "react-markdown": "^10.1.0",
@@ -86,7 +85,6 @@
         "@types/react-collapse": "^5.0.4",
         "@types/react-color": "^3.0.13",
         "@types/react-dom": "^19.1.9",
-        "@types/react-file-reader-input": "^2.0.4",
         "@types/string-hash": "^1.1.3",
         "@types/uuid": "^10.0.0",
         "@types/wicg-file-system-access": "^2023.10.6",
@@ -3225,15 +3223,6 @@
         "@types/react": "^19.0.0"
       }
     },
-    "node_modules/@types/react-file-reader-input": {
-      "version": "2.0.4",
-      "resolved": "https://registry.npmjs.org/@types/react-file-reader-input/-/react-file-reader-input-2.0.4.tgz",
-      "integrity": "sha512-Jqrfn+w42j8t8Q3npMXXKPdk+reIM0UHLKVc3ykrA7q7bN3Z62SGhsClZX0+Edlqm66lcKwmDQl+WMm+Xor7Xg==",
-      "dev": true,
-      "dependencies": {
-        "@types/react": "*"
-      }
-    },
     "node_modules/@types/reactcss": {
       "version": "1.2.12",
       "resolved": "https://registry.npmjs.org/@types/reactcss/-/reactcss-1.2.12.tgz",
@@ -11681,15 +11670,6 @@
         "react": "^19.1.1"
       }
     },
-    "node_modules/react-file-reader-input": {
-      "version": "2.0.0",
-      "resolved": "https://registry.npmjs.org/react-file-reader-input/-/react-file-reader-input-2.0.0.tgz",
-      "integrity": "sha512-1XgkCpwMnNQsuOIy938UCntz8Xzwt9ECwHaH3cCfIQK1SPpH+y7gCYtqEcb6Rm0hAUq7Lp9+Ljoti9zGMswYrQ==",
-      "peerDependencies": {
-        "react": "^15.0.0 || ^16.0.0",
-        "react-dom": "^15.0.0 || ^16.0.0"
-      }
-    },
     "node_modules/react-hot-loader": {
       "version": "4.13.1",
       "resolved": "https://registry.npmjs.org/react-hot-loader/-/react-hot-loader-4.13.1.tgz",