docs: add privacy policy link to footer

[Sullyvahnn-v2]

Summary

• Adds a Privacy Policy link in the docs site footer
• Centers footer copyright content
• Fixes footer bottom padding and landing footer spacing across breakpoints

Test Plan

• Confirm the footer shows the Privacy Policy link and opens https://swmansion.com/privacy/policy/ in a new tab
• Check copyright text is centered on desktop and mobile
• Verify footer padding looks correct at common widths (desktop, tablet, phone)
• On the landing page, confirm footer/background spacing still lines up after the layout tweaks

[github-actions]

WPT non-regression comparison

PASS — no regressions · 1 improved section(s) · overall 2589 → 2632 (+43)

Spec section	Base pass	Head pass	Delta
BiquadFilterNode	232	275	+43

Unchanged sections (27)

Spec section	Base pass	Head pass	Delta
Processing model	0	0	0
Other	52	52	0
AnalyserNode	138	138	0
AudioBuffer	140	140	0
AudioBufferSourceNode	208	208	0
AudioContext	58	58	0
AudioNode	261	261	0
AudioParam	599	599	0
ChannelMergerNode	30	30	0
ChannelSplitterNode	7	7	0
ConstantSourceNode	59	59	0
ConvolverNode	170	170	0
DelayNode	104	104	0
DestinationNode	0	0	0
DynamicsCompressorNode	4	4	0
GainNode	15	15	0
IIRFilterNode	87	87	0
MediaElementAudioSourceNode	0	0	0
MediaStreamAudioDestinationNode	1	1	0
MediaStreamAudioSourceNode	0	0	0
OfflineAudioContext	35	35	0
OscillatorNode	104	104	0
PannerNode	75	75	0
PeriodicWave	33	33	0
ScriptProcessorNode	0	0	0
StereoPannerNode	102	102	0
WaveShaperNode	75	75	0

_{Baseline: fd1d87dca04244c53abfbddf8ab98284cb3218ee · Candidate: 91dbbc34c142f5d04793b20c0f9644f16cdf2da3}

_{Workflow run · this comment is updated on every push.}

[p-malecki]

pls review comment