docs: use /app as standard example working directory (#1254)

Author: MikeMcC399

base/README.md

@@ -29,10 +29,10 @@ In this example we first run the unchanged image `cypress/base` as a container:
 ```shell
 cd examples/basic         # Use a pre-configured simple Cypress E2E project
 npm ci                    # Install Cypress
-docker run -it --rm -v .:/e2e -w /e2e cypress/base  # Run image as container
+docker run -it --rm -v .:/app -w /app cypress/base  # Run image as container
 ```
 
-At the `bash` prompt `:/e2e#`, we can then enter the following commands:
+At the `bash` prompt `:/app#`, we can then enter the following commands:
 
 ```shell
 npx cypress install       # Install Cypress binary into running Docker container

browsers/README.md

@@ -34,10 +34,10 @@ In this example we first run the unchanged image `cypress/browsers` as a contain
 ```shell
 cd examples/basic         # Use a pre-configured simple Cypress E2E project
 npm ci                    # Install Cypress
-docker run -it --rm -v .:/e2e -w /e2e cypress/browsers  # Run image as container
+docker run -it --rm -v .:/app -w /app cypress/browsers  # Run image as container
 ```
 
-At the `bash` prompt `:/e2e#`, we can then enter the following commands:
+At the `bash` prompt `:/app#`, we can then enter the following commands:
 
 ```shell
 npx cypress install       # Install Cypress binary into running Docker container

examples/chromium/README.md

@@ -26,10 +26,10 @@ In this example we first run the unchanged image `cypress/base` as a container:
 ```shell
 cd examples/chromium  # Use a pre-configured simple Cypress E2E project
 npm ci                # Install Cypress
-docker run -it --rm -v .:/e2e -w /e2e cypress/base  # Run image as container
+docker run -it --rm -v .:/app -w /app cypress/base  # Run image as container
 ```
 
-At the `bash` prompt `:/e2e#`, we can then enter the following commands:
+At the `bash` prompt `:/app#`, we can then enter the following commands:
 
 ```shell
 apt-get update                      # Update package index

examples/firefox-esr/README.md

@@ -28,10 +28,10 @@ In this example we first run the unchanged image `cypress/base` as a container:
 ```shell
 cd examples/firefox-esr  # Use a pre-configured simple Cypress E2E project
 npm ci                # Install Cypress
-docker run -it --rm -v .:/e2e -w /e2e cypress/base  # Run image as container
+docker run -it --rm -v .:/app -w /app cypress/base  # Run image as container
 ```
 
-At the `bash` prompt `:/e2e#`, we can then enter the following commands:
+At the `bash` prompt `:/app#`, we can then enter the following commands:
 
 ```shell
 apt-get update                     # Update package index