Add brand and design guidelines

[pavithraes]

Addresses #561
Closes conda-incubator/conda-store-ui#344

Description

This pull request:

• Documents quick ref for brand guidelines
• Adds logos and brand guidelines PDF
• Documents the UI/UX design system: https://hackmd.io/@S1meqA60T5ycyQ3qIxy4GA/condadesignsystem

Pull request checklist

• Did you test this change locally?
• Did you update the documentation (if required)?
• Did you add/update relevant tests for this change (if required)? N/A

Additional information

For reviewers, documentation preview: https://deploy-preview-701--kaleidoscopic-dango-0cf31d.netlify.app/community/design

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[trallard]

Thank you @pavithraes and @smeragoel! This looks good to me.
Will make sure to add @smeragoel as co-author to this PR before merging

[nkaretnikov]

@trallard The linter failures on this PR were real:

fix end of files.........................................................Failed
- hook id: end-of-file-fixer
- exit code: 1
- files were modified by this hook

Fixing docusaurus-docs/community/assets/logos/conda-store-logo-horizontal-lockup.svg
Fixing docusaurus-docs/community/assets/logos/conda-store-symbol-only.svg
Fixing docusaurus-docs/community/assets/logos/conda-store-logo-vertical-lockup.svg

The linter needs to be configured to skip this directory.