Add blog post "FerretDB Demo: Launch and Test a Database in Minutes"

[Fashander]

Description

Readiness checklist

• I added/updated unit tests.
• I added/updated integration/compatibility tests.
• I added/updated comments and checked rendering.
• I made spot refactorings.
• I updated user documentation.
• I ran task all, and it passed.
• I ensured that PR title is good enough for the changelog.
• (for maintainers only) I set Reviewers (@FerretDB/core), Labels, Project and project's Sprint fields.
• I marked all done items in this checklist.

[mergify]

Marketing blog posts should be reviewed by @ptrfarkas and @AlekSi.

[codecov]

Codecov Report

Merging #2851 (7f77a9d) into main (f4bb3f3) will not change coverage.
The diff coverage is n/a.

❗ Current head 7f77a9d differs from pull request most recent head 0dbb900. Consider uploading reports for the commit 0dbb900 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2851   +/-   ##
=======================================
  Coverage   63.45%   63.45%           
=======================================
  Files         451      451           
  Lines       23417    23417           
=======================================
  Hits        14860    14860           
  Misses       7591     7591           
  Partials      966      966           

Flag	Coverage Δ
integration	56.66% <ø> (ø)
mongodb	4.17% <ø> (ø)
pg	56.58% <ø> (ø)
shard-1	40.95% <ø> (ø)
shard-2	41.75% <ø> (ø)
shard-3	45.12% <ø> (+0.10%)	⬆️
unit	24.43% <ø> (+0.02%)	⬆️

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[Fashander]

@ptrfarkas PTAL