Fix typo in GitHub and StackOverflow

[alexandear]

Github -> GitHub

Stackoverflow -> StackOverflow

[Copilot]

Pull request overview

This PR standardizes brand capitalization in community documentation by correcting “Github” to “GitHub” and “Stackoverflow” to “StackOverflow” across governance and contributor-facing markdown files.

Changes:

• Fix “Github” → “GitHub” in governance, contributor ladder, and multiple contributor/election listings.
• Fix “Stackoverflow” → “StackOverflow” in CONTRIBUTING.md.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
governance.md	Corrects “Github” to “GitHub” in governance wording.
elections/steering-committee-election-2025.md	Updates the table header to “GitHub Handle”.
contributors/organization_members.md	Updates table headers to “GitHub Handle” in both member sections.
contributors/maintainers.md	Updates table headers to “GitHub Handle” in both maintainer sections.
contributors/core_contributors.md	Updates table headers to “GitHub Handle” in both contributor sections.
contributor_ladder.md	Fixes “Github” to “GitHub” in inactivity definition.
CONTRIBUTING.md	Fixes “Github” to “GitHub” and “Stackoverflow” to “StackOverflow” in contributor guidance.

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