[Docs] Add language identifiers to fenced code blocks (#28955)

Add language identifiers to code blocks

templates/adding_a_new_example_script/README.md

@@ -18,13 +18,13 @@ limitations under the License.
 
 This folder provide a template for adding a new example script implementing a training or inference task with the
 models in the 🤗 Transformers library. To use it, you will need to install cookiecutter:
-```
+```bash
 pip install cookiecutter
 ```
 or refer to the installation page of the [cookiecutter documentation](https://cookiecutter.readthedocs.io/).
 
 You can then run the following command inside the `examples` folder of the transformers repo:
-```
+```bash
 cookiecutter ../templates/adding_a_new_example_script/
 ```
 and answer the questions asked, which will generate a new folder where you will find a pre-filled template for your

templates/adding_a_new_model/ADD_NEW_MODEL_PROPOSAL_TEMPLATE.md

@@ -582,27 +582,27 @@ You should do the following:
 
 1.  Create a branch with a descriptive name from your main branch
 
-```
+```bash
     git checkout -b add_[lowercase name of model]
 ```
 
 2.  Commit the automatically generated code:
 
-```
+```bash
     git add .
     git commit
 ```
 
 3.  Fetch and rebase to current main
 
-```
+```bash
     git fetch upstream
     git rebase upstream/main
 ```
 
 4.  Push the changes to your account using:
 
-```
+```bash
     git push -u origin a-descriptive-name-for-my-changes
 ```
 

templates/adding_a_new_model/README.md

@@ -103,7 +103,7 @@ tests/test_modeling_tf_<model_name>.py
 
 You can run the tests to ensure that they all pass:
 
-```
+```bash
 python -m pytest ./tests/test_*<model_name>*.py
 ```
 
@@ -236,7 +236,7 @@ depending on your choices).
 
 You will also see a doc file and tests for your new models. First you should run
 
-```
+```bash
 make style
 make fix-copies
 ```
@@ -247,7 +247,7 @@ and then you can start tweaking your model. You should:
 
 Once you're done, you can run the tests to ensure that they all pass:
 
-```
+```bash
 python -m pytest ./tests/test_*<model_name>*.py
 ```
 

templates/adding_a_new_model/open_model_proposals/ADD_BIG_BIRD.md

@@ -593,27 +593,27 @@ You should do the following:
 
 1.  Create a branch with a descriptive name from your main branch
 
-```
+```bash
     git checkout -b add_big_bird
 ```
 
 2.  Commit the automatically generated code:
 
-```
+```bash
     git add .
     git commit
 ```
 
 3.  Fetch and rebase to current main
 
-```
+```bash
     git fetch upstream
     git rebase upstream/main
 ```
 
 4.  Push the changes to your account using:
 
-```
+```bash
     git push -u origin a-descriptive-name-for-my-changes
 ```