fix yaml requirement & readme link

README.rst

@@ -52,7 +52,7 @@ E.g.
 ``tkldev-detective lint zoneminder``
 
 For more information on how it works and how to develop more functionality, see
-`overview`_, `custom modules`_ and `tools and tricks.rst`_
+`overview`_, `custom modules`_ and `tools and tricks`_
 
 Copyright
 ---------

tkldet_modules/yaml_check.py

@@ -14,14 +14,17 @@
 #
 # You should have received a copy of the GNU General Public License along with
 # tkldev-detective. If not, see <https://www.gnu.org/licenses/>.
-import yaml
+try:
+    import yaml
+except ImportError:
+    YAML = False
+else:
+    YAML = True
 from typing import Generator
 
 from libtkldet.linter import FileLinter, FileItem, register_linter
 from libtkldet.report import Report, FileReport, ReportLevel
 
-
-@register_linter
 class YamlLinter(FileLinter):
     ENABLE_TAGS: set[str] = {"ext:yaml", "ext:yml"}
     DISABLE_TAGS: set[str] = set()
@@ -55,3 +58,6 @@ def check(self, item: FileItem) -> Generator[Report, None, None]:
                     source="yaml_check",
                     level=ReportLevel.ERROR,
                 )
+
+if YAML:
+    register_linter(YamlLinter)