Specify exact path of dependency license metadata cache in ignore files

The "Check Dependencies" templates store a cache of metadata about the licenses of dependencies under the `.licenses`
folder. The templates use the default location for this folder, under the root of the repository.

Since this folder only contains generated files, it should be excluded from the validation checks performed by unrelated
tools.

Previously, the markdownlint and Prettier ignore configurations for this folder did not explicitly specify a location in
the root of the repository, meaning that it would result in ignoring a folder of that name at any location in the
project. In cases like this where a specific path is known, it is best to configure that exact path in order to avoid
any chance of unexpected behavior.

Author: per1234

.markdownlintignore

@@ -1,5 +1,5 @@
 # Source: https://github.com/arduino/tooling-project-assets/blob/main/workflow-templates/assets/check-markdown/.markdownlintignore
-.licenses/
+/.licenses/
 __pycache__/
 node_modules/
 /other/clang-format-configuration/testdata/golden/samples/

.prettierignore

@@ -1,4 +1,4 @@
-.licenses/
+/.licenses/
 __pycache__/
 node_modules/
 /other/clang-format-configuration/testdata/golden/samples/

workflow-templates/assets/check-markdown/.markdownlintignore

@@ -1,4 +1,4 @@
 # Source: https://github.com/arduino/tooling-project-assets/blob/main/workflow-templates/assets/check-markdown/.markdownlintignore
-.licenses/
+/.licenses/
 __pycache__/
 node_modules/

workflow-templates/assets/check-prettier-formatting/.prettierignore

@@ -1,4 +1,4 @@
-.licenses/
+/.licenses/
 __pycache__/
 node_modules/
 poetry.lock