Molfile Input, Text editor for other descriptions, text template updated docs

[alizaib1217]

This PR has docs for the following;

• Molfile input (details.mdx, new molfile_input.png) — the Chemical
  identifiers paragraph said the Molfile field was copy-only and could not create a
  Sample. You can now paste a molfile or upload a .mol / .sdf file and save it
  without opening Ketcher. Covers paste, upload, multi-structure files, and the
  validation message. Matches ComPlat/chemotion_ELN issue feat: mixture documentation is added #396.
• Where the text editor appears (text_editor.mdx) — added the list of places
  you actually get it: reaction description, purification details, screen and
  wellplate descriptions, research plan rich text, and analysis descriptions.
• Font Awesome version (text_templates.mdx) — the icon link points at v4, so
  the text now says Font Awesome 4. Picking a v5 or v6 icon class does not work.