Random small bug fixes

[tiiavalt]

Describe the bug
Let's find and fix small bugs around the project, e.g. accessibility, style and other bugs that are too small to fix one by one in their own issues.

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The result

Added:

• aria-labels for offsetButtons
• default case for breadcrumbs’ switch case

Deleted:

• file: KeywordAnalysisTable.styles.js

Fixed:

• checkbox container’s border color
• front page’s icons’ sizes and margins
• footer’s height and add some margin, and fixed the logo’s accessibility
• breadcrumbs’ aria-labels
• table’s scroll buttons’ aria-label
• pie charts’ styles and header level
• tabs’ active link’s hover
• accordion’s first th’s width
• table th’s margin

Removed:

• redundant titles
• duplicate ‘main’
• redundant class ‘underline’
• redundant ‘!important’s
• redundant text-decoration from links, because it’s already a default style
• redundant aria-label and content and hid duplicate content from screen reader

Other:

• replaced pixels with css variables
• external links open now in a new tab