"Hot posts" sidebar widget should render Markdown in titles

[Oaphi]

A followup to #1860 - forgot to add title rendering to the widget. The PR also makes the widget itself a partial (reuse + code organization):

Since the widget is cached, it is advised to clear cache when testing

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.04%. Comparing base (c6816f9) to head (ae19a27).
⚠️ Report is 12 commits behind head on develop.

Additional details and impacted files

Components	Coverage Δ
controllers	73.14% <ø> (ø)
helpers	84.16% <ø> (-0.51%)	⬇️
jobs	60.86% <ø> (ø)
models	89.25% <ø> (ø)
tasks	61.11% <ø> (ø)

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