feat(wakatime): split insights into separate language and editor sections

[thisisrick25]

Splits the single insights config key into two independent keys for granular control:

• insightsLanguages -> insights/languages/last_year
• insightsEditors -> insights/editors/last_year

The section config now supports 5 keys: last30, allTime, sinceToday, insightsLanguages, insightsEditors. Default remains ['last30'] when sections is unset. Sections render in config order; only selected endpoints are fetched; graceful per-section degradation preserved.

• Updated SectionKey union + VALID_SECTIONS
• Split renderInsights into renderInsightsLanguages (#### Last Year Languages) + renderInsightsEditors (#### Last Year Editors)
• Updated exhaustive renderSection switch
• Updated plugin README sections table, note, example output, and config example
• Verified: npm run build exit 0, npx tsc --noEmit exit 0