feat: Create separate page for Pastebins

[redoomed1]

Changes proposed in this PR:

• Create a separate recommendation page for pastebins
  • This PR kicks off a multipart effort to address #2596
  • No changes to the content ported from the Productivity Tools page
  • Changes for the new recommendation page
  • Added page cover: a photo by Chris Ried at https://unsplash.com/photos/a-computer-screen-with-a-bunch-of-code-on-it-ieic5Tq8YMk; any suggestions for alternative page covers are welcome!
  • Added content-paste Material Design sidebar icon
  • Added page introduction and one-sentence description
• Add Pastebins section in tools.md and move PrivateBin entry to it
• Delete "Paste services" section from the Productivity Tools page

This is my first PR that involves an image upload, so I welcome any feedback in this department! I went over https://www.privacyguides.org/en/meta/uploading-images, but there isn't any guidance on WebP images, which is the preferred format for cover images.

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[redoomed1]

How I went about optimizing the Unsplash image linked in my initial post:

1. Download it as a .jpg file
2. Use cwebp to convert it to a WebP file by running cwebp -size 300000 [image-name].jpg -o pastebins.webp

-size specifies target size in bytes. I set it to 300,000 bytes (300 KB) because, of all the cover images on the site, the one for the Desktop Browsers page is the largest at 305 KB.

[jonaharagon]

Good note, we should probably document WebP optimization. IIRC all the existing images were a pre-set quality level but I don't remember what that setting was. I'll do that later.