Encapsulate all multiline strings in triple-quotes in Gherkin files

Since pytest-bdd v8.0.0 uses the official Gherkin parser, multiline
strings must now be encapsulated by triple-quotes.

See:
- https://pytest-bdd.readthedocs.io/en/stable/#id2
- https://pytest-bdd.readthedocs.io/en/stable/#docstrings

tests/bdd/features/template.feature

@@ -2,12 +2,13 @@
 # License: https://www.gnu.org/licenses/gpl-3.0.html
 
 Feature: Using templates
-
     Scenario Outline: Template contents should be used in new entry
         Given we use the config "<config_file>"
         And we use the password "test" if prompted
         And we append to the editor if opened
+            """
             This is an addition to a templated entry
+            """
         When we run "jrnl --config-override template features/templates/basic.template"
         And we run "jrnl -1"
         Then the output should contain "This text is in the basic template"