docs: add link to flow parallelization

[cristianmtr]

No description provided.

[JoanFM]

We will add this after PR #3535 is merged, and the concepts are aligned and clarified

[github-actions]

Latency summary

Current PR yields:

• 🐎🐎🐎🐎 index QPS at 1429, delta to last 2 avg.: +14%
• 🐎🐎🐎🐎 query QPS at 63, delta to last 2 avg.: +21%
• 🐎🐎🐎🐎 dam extend QPS at 56308, delta to last 2 avg.: +34%
• 🐎🐎🐎🐎 avg flow time within 1.3759 seconds, delta to last 2 avg.: -18%
• 🐢🐢 import jina within 0.3488 seconds, delta to last 2 avg.: -8%

Breakdown

Version	Index QPS	Query QPS	DAM Extend QPS	Avg Flow Time (s)	Import Time (s)
current	1429	63	56308	1.3759	0.3488
2.1.5	1349	57	42902	1.6913	0.3508
2.1.4	1137	45	40752	1.6874	0.4117

Backed by latency-tracking. Further commits will update this comment.

[codecov]

Codecov Report

Merging #3597 (74aa5ea) into master (abd8e6c) will decrease coverage by 0.52%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3597      +/-   ##
==========================================
- Coverage   89.19%   88.67%   -0.53%     
==========================================
  Files         151      154       +3     
  Lines       11243    11527     +284     
==========================================
+ Hits        10028    10221     +193     
- Misses       1215     1306      +91     

Flag	Coverage Δ
daemon	45.08% <ø> (-0.42%)	⬇️
jina	88.60% <ø> (-0.52%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
jina/peapods/pods/k8s.py	60.92% <0.00%> (-31.08%)	⬇️
jina/peapods/pods/compound.py	82.71% <0.00%> (-7.63%)	⬇️
jina/peapods/pods/k8slib/kubernetes_tools.py	72.72% <0.00%> (-6.99%)	⬇️
jina/peapods/runtimes/gateway/websocket/app.py	85.41% <0.00%> (-3.72%)	⬇️
jina/types/arrays/abstract.py	65.38% <0.00%> (-3.59%)	⬇️
jina/peapods/runtimes/container/__init__.py	80.12% <0.00%> (-1.75%)	⬇️
jina/hubble/hubapi.py	96.00% <0.00%> (-0.94%)	⬇️
jina/helper.py	82.76% <0.00%> (-0.36%)	⬇️
jina/flow/base.py	87.92% <0.00%> (-0.33%)	⬇️
jina/peapods/runtimes/gateway/prefetch.py
... and 26 more

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