Fix typos

Author: mcbarton

CONTRIBUTING.md

@@ -190,13 +190,13 @@ will run the xeus-cpp-lite-demo.ipynb notebook in chrome, with the C++20 kernel,
 and stop the script, if the notebook has finished running after 200 seconds. This works for Safari, Chrome and Firefox. It should be noted
 that in the case of Safari, safari driver  must be enabled, and downloads must be enabled from 127.0.0.1 . Once the script has finished
 executing you can compare the notebook download from the one in the repo, to check the deployment works as expected, by executing
-(replace notebok_run with the notebook chosen for the Python script)
+(replace notebook_run with the notebook chosen for the Python script)
 
 ```bash
 nbdiff notebook_run $HOME/Downlaods/notebook_run
 ```
 
-For example after running the above test command, to test no changes have occured, execute
+For example after running the above test command, to test no changes have occurred, execute
 
 ```bash
 nbdiff xeus-cpp-lite-demo.ipynb $HOME/Downlaods/xeus-cpp-lite-demo.ipynb

README.md

@@ -206,13 +206,13 @@ will run the xeus-cpp-lite-demo.ipynb notebook in chrome, with the C++20 kernel,
 and stop the script, if the notebook has finished running after 200 seconds. This works for Safari, Chrome and Firefox. It should be noted
 that in the case of Safari, safari driver  must be enabled, and downloads must be enabled from 127.0.0.1 . Once the script has finished
 executing you can compare the notebook download from the one in the repo, to check the deployment works as expected, by executing
-(replace notebok_run with the notebook chosen for the Python script)
+(replace notebook_run with the notebook chosen for the Python script)
 
 ```bash
 nbdiff notebook_run $HOME/Downlaods/notebook_run
 ```
 
-For example after running the above test command, to test no changes have occured, execute
+For example after running the above test command, to test no changes have occurred, execute
 
 ```bash
 nbdiff xeus-cpp-lite-demo.ipynb $HOME/Downlaods/xeus-cpp-lite-demo.ipynb

docs/source/InstallationAndUsage.rst

@@ -187,14 +187,14 @@ will run the xeus-cpp-lite-demo.ipynb notebook in chrome, with the C++20 kernel,
 and stop the script, if the notebook has finished running after 200 seconds. This works for Safari, Chrome and Firefox. It should be noted
 that in the case of Safari, safari driver  must be enabled, and downloads must be enabled from 127.0.0.1 . Once the script has finished
 executing you can compare the notebook download from the one in the repo, to check the deployment works as expected, by executing
-(replace notebok_run with the notebook chosen for the Python script)
+(replace notebook_run with the notebook chosen for the Python script)
 
 .. code-block:: bash
 
     nbdiff notebook_run $HOME/Downlaods/notebook_run
 
 
-For example after running the above test command, to test no changes have occured, execute
+For example after running the above test command, to test no changes have occurred, execute
 
 .. code-block:: bash