web: improve style for mobile view

[duhow]

Make the website more mobile-friendly - note the main menu needs another change (not to do on this PR).

Changes

• ❗ In cb09e96 , the unused code style from original CSS style is removed.
• Added .adapt class to <form> , this way we skip the page Access Level Configuration, which currently has an acceptable view layout for phone.
• 🆕 Inputs are set to display: block, underneath the previous cell.
• In fa61c0c , update ConfirmationHtml function to use HeaderHtml function, this way, when the user updates configuration, it will use style CSS, and the page won't render as a blank website.

NOTE: While I separated the content into a new file style.css, bear in mind this is not integrated into build process.
I am using https://www.freeformatter.com/css-minifier.html to minify the CSS file and copying the content back again to the header file as const. You can request to delete the new style.css file if you wish.

[iranl]

I don't have a problem with adding the unminified style.css, but would not place it in src. I would put it somewhere on the top level, maybe add a resources dir or something where how-to-flash.txt and boot_app0.bin could also live.

[duhow]

Mmmm.. what about include ? If not, resources sounds also ok.

[iranl]

include has special purpose in platformio, so I wouldn't use it for other purposes

[duhow]

@iranl check now? 🙏🏻