Rename roadmap -> roadmaps in docs

[sfmig]

Description

What is this PR

• [ ] Bug fix
• [ ] Addition of a new feature
• [x] Other

Why is this PR needed? For future-proofing, we decided to have in our docs a link to all our roadmaps (similar to brainglobe).

What does this PR do?

• Renames the title of the Roadmaps site to be in plural.
• Renames the .md file itself and the associated target variable for consistency.

References

\

How has this PR been tested?

Tests pass locally and in CI, docs build locally.

Is this a breaking change?

\

Does this PR require an update to the documentation?

\

Checklist:

• [x] The code has been tested locally
• [ n/a ] Tests have been added to cover all new functionality
• [ n/a ] The documentation has been updated to reflect any changes
• [x] The code has been formatted with pre-commit

[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
No data about Duplication

See analysis details on SonarCloud

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 99.68%. Comparing base (b2de775) to head (a92460f).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #188 +/- ## ======================================= Coverage 99.68% 99.68% ======================================= Files 11 11 Lines 638 638 ======================================= Hits 636 636 Misses 2 2 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.