Update eslint config to include unused imports and indenting

[rmccar]

What is the context of this PR?

Fixes: #3049

Updates the eslint config to automatically fix indenting and unused imports for .js files.
Also adds a vscode recommended settings section to readme.

This sets the indenting for js files at 2 spaces just because thats what we have currently. We use 4 spaces for other files such as the nunjucks ones. We should have a discussion before this is merged to decide on what we think is the right level of indenting. Personally I prefer 4 spaces as I think it is more readable. Decided to keep it as it is for now and have a think about whether we want to move to 4 spaces in a future PR.

Ran linters on all of our js files and also added changes to this pr to establish a baseline.

Had to disable the indenting rule in a couple of test files where we were using a render component function in the middle of a string. This was causing some indentation issues.

How to review this PR

• Checkout this PR
• Make some changes to a js file which includes making indenting errors and adding imports in that aren't being used
• Create a new branch from this one with the changes and try committing
• See that the indenting and imports are automatically fixed

Checklist

This needs to be completed by the person raising the PR.

• I have selected the correct Assignee
• I have linked the correct Issue

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