docs(README): Minor fixes

[PLNech]

• Updated banner alt-text
• Updated License link
• Removed "Made by [Algolia]" (seems redundant as hosted under github.com/algolia)
• Remove simply from the install instructions (especially as you already say it's a "simple" [...] "dependency manager")
• Use ordered lists (https://github.com/adam-p/markdown-here/wiki/Markdown-Cheatsheet)
• Linkify license

[spinach]

Thanks @PLNech !