docs: add ZeeD26 as a contributor (#519)

* docs: update README.md [skip ci]

* docs: update .all-contributorsrc [skip ci]

Co-authored-by: allcontributors[bot] <46447321+allcontributors[bot]@users.noreply.github.com>

.all-contributorsrc

@@ -413,6 +413,15 @@
       "contributions": [
         "code"
       ]
+    },
+    {
+      "login": "ZeeD26",
+      "name": "Dominik Steinberger",
+      "avatar_url": "https://avatars2.githubusercontent.com/u/2487468?v=4",
+      "profile": "https://github.com/ZeeD26",
+      "contributions": [
+        "code"
+      ]
     }
   ],
   "contributorsPerLine": 7,

README.md

@@ -958,6 +958,7 @@ This project was created by [Henry Schreiner](https://github.com/henryiii) and m
   </tr>
   <tr>
     <td align="center"><a href="https://github.com/jakoblover"><img src="https://avatars0.githubusercontent.com/u/14160441?v=4" width="100px;" alt=""/><br /><sub><b>Jakob Lover</b></sub></a><br /><a href="https://github.com/CLIUtils/CLI11/commits?author=jakoblover" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/ZeeD26"><img src="https://avatars2.githubusercontent.com/u/2487468?v=4" width="100px;" alt=""/><br /><sub><b>Dominik Steinberger</b></sub></a><br /><a href="https://github.com/CLIUtils/CLI11/commits?author=ZeeD26" title="Code">💻</a></td>
   </tr>
 </table>
 

include/CLI/Validators.hpp

@@ -746,9 +746,7 @@ class IsMember : public Validator {
             }
 
             // If you reach this point, the result was not found
-            std::string out(" not in ");
-            out += detail::generate_set(detail::smart_deref(set));
-            return out;
+            return input + " not in " + detail::generate_set(detail::smart_deref(set));
         };
     }