renamed "extra" from hyperlink to richtext

also, attempt to install toot with richtext "extra"
when building on github

.github/workflows/test.yml

@@ -18,7 +18,7 @@ jobs:
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip
-          pip install -e .
+          pip install -e .\[richtext\]
           pip install -r requirements-test.txt
       - name: Run tests
         run: |

setup.py

@@ -41,7 +41,7 @@
         "tomlkit>=0.10.0,<1.0"
     ],
     extras_require={
-        "hyperlinks": ['urwidgets>=0.1,<0.2'],
+        "richtext": ['urwidgets>=0.1,<0.2'],
     },
     entry_points={
         'console_scripts': [