Please ad a Label to the Edit Field and Text to the Run Button in the py-repl Component

[frastlin]

Hello,
I'm a screen reader user and noticed that the py-repl component is missing text in its button component for run. There is the multiline text field for typing code (that should also have a <label> element, then there is an empty <button></button> tag with some CSS to show the run command.

1. Visit: the blog post with an example
2. Select all on the page and copy, then paste into a text editor
3. Find the text: "such as <py-script> and <py-env>."
4. Observe that between the above text and "Since we already loaded pandas and numpy", there are just blank spaces. This is pretty much how it looks to a screen reader user.

To fix this, please add a label to the multiline input field saying something like: "Python Script Area" and text to the run button saying something like: "Run".

[fpliger]

this should have been closed by #322