docs: Standardize landing page format

[geoffreynyaga]

This PR updates the landing page (specifically the "In this documentation" section) to align with the standardized format used across other canonical products , improving consistency and user experience.

Changes Made

• Replaced markdown table with a responsive grid layout (and cards) for and aligning to design patterns of other canonical products.

Reference implementation

The new format follows the same structure as other canonical product documentation:
• Chisel docs
• Ubuntu server docs

Testing

• Verified layout renders correctly across different screen sizes
• Confirmed all links and navigation elements function properly

Screenshots

Before

After

MULTI-2031

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.44%. Comparing base (408f122) to head (7ad0ab1).
⚠️ Report is 124 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4170      +/-   ##
==========================================
+ Coverage   89.35%   89.44%   +0.09%     
==========================================
  Files         259      260       +1     
  Lines       15743    15818      +75     
==========================================
+ Hits        14067    14149      +82     
+ Misses       1676     1669       -7     

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[msuchane]

Reviewed, looks good.

I'm using a slightly different syntax on Desktop, but the end result should be the same. Adding just for reference:

::::{grid} 1 1 2 2

:::{grid-item-card} Tutorial
:link: /tutorial/index
:link-type: doc

**Get started**: a hands-on introduction to Ubuntu Desktop for new users
:::

:::{grid-item-card} How-to guides
:link: /how-to/index
:link-type: doc

**Step-by-step guides** covering key operations and common tasks
:::
::::

Note two differences:

• I'm using colon-fenced blocks. Thanks to them, I get some syntax highlighting within the blocks that would otherwise be obscured by the code block. No functional difference other than that.

• I'm using a different way to specify the page link. I honestly don't know whether to prefer one or the other. Both notations report a build error when the link is broken, so they should be the same.

[Sploder12]

LGTM! Page looks nice and links work

[sharder996]

@geoffreynyaga One small, real linting error this time 😸

[sharder996]

One small, real linting error this time 😸

@geoffreynyaga

[sharder996]

Thanks, @geoffreynyaga!