README: Consistently replace shell fence with bash

Consistently replace every 'shell' or 'sh' code block fences use with a
'bash' one. Do so as the latter is used in a majority of blocks already,
in this ./README.md file that is.

Signed-off-by: Marco Miller <marco.miller@ericsson.com>

README.md

@@ -75,13 +75,13 @@ You can also run two scripts to watch for changes and rebuild automatically:
 
 1. From the root, run:
 
-   ```sh
+   ```bash
    yarn tswatch # to compile TypeScript files
    ```
 
 2. In parallel, run:
 
-   ```sh
+   ```bash
    cd examples/<browser or electron>
    yarn watch # to update the frontend bundles (loaded by the browser)
    ```
@@ -317,20 +317,20 @@ If there is no notification, you can open the application directly in the **Remo
 
 To run tests once, at the root of the project, run:
 
-```shell
+```bash
 yarn test --verbose
 ```
 
 To keep tests running, use:
 
-```shell
+```bash
 yarn test --verbose --watch
 ```
 
 ### Test coverage
 
 The following command prints a coverage report to the terminal. As of now, it covers all typescript files of the project, including those that are not supposed to have tests.
 
-```shell
+```bash
 yarn test --coverage --collectCoverageFrom='src/**/*.ts'
 ```