docs: Small updates to the formatting of the README.

[skyzyx]

Description

• GitHub has deprecated the old dark/light-mode image trick with the use of <picture> and prefers-color-scheme media queries. Performed the requisite updates.
• When referencing other projects, link the first usage of its name to its website.
• Streamline the instructions in the README to allow for fewer steps.
• When documenting CLI commands, clarity should always prevail in order to improve understanding. In this case, expanded npm i (which one may prefer to type) to the equivalent npm install (which provides greater clarity about what the command will do).
• Added some configuration files which make it easier for VS Code users to begin contributing with recommended settings and extensions installed. (Unlike JetBrains IDEs, the .vscode directory is meant to be committed as it contains project-wide configurations.)
• Enable users of certain kinds of tooling (e.g., Markdownlint, EditorConfig) to add files to the repository to disable those configs when they are configured to run automatically via LSP server.
• The spec-compliant way to annotate a URL is to wrap it in angle brackets. Although GitHub-Formatted Markdown (GFM) extends the spec with custom functionality, this is not supported as part of standard Commonmark, so it may not work elsewhere.
• In a numbered or bulleted list, indenting code blocks under the list item will correctly indent and maintain the numbering of a Markdown list. (source)

Motivation and Context

• Improve the getting-started experience for brand-new users.
• Improve the getting-started experience for VS Code users.
• Improve the ability to quickly understand what things are and how to run them.

Types of changes

• Documentation
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My change depends on a change in the main opentofu repository.

[abstractionfactory]

Thank you @skyzyx !