Adds referrals to gitcoin quests landing page

[owocki]

Adds referral functionality to gitcoin quests landing page.

[codecov]

Codecov Report

Merging #5297 into master will increase coverage by 0.3%.
The diff coverage is 26.66%.

@@            Coverage Diff            @@
##           master    #5297     +/-   ##
=========================================
+ Coverage   29.89%   30.19%   +0.3%     
=========================================
  Files         231      231             
  Lines       19138    19575    +437     
  Branches     2736     2819     +83     
=========================================
+ Hits         5721     5911    +190     
- Misses      13178    13411    +233     
- Partials      239      253     +14

Impacted Files	Coverage Δ
app/quests/admin.py	100% <100%> (ø)	⬆️
app/dashboard/admin.py	63.09% <100%> (ø)	⬆️
app/quests/views.py	19.56% <11.9%> (-3.21%)	⬇️
app/marketing/utils.py	28.41% <5.88%> (-2.54%)	⬇️
app/dashboard/models.py	50.02% <66.66%> (+0.02%)	⬆️
app/quests/models.py	47.12% <83.33%> (+2.68%)	⬆️
app/bounty_requests/forms.py	50% <0%> (-3.85%)	⬇️
app/bounty_requests/views.py	29.62% <0%> (-0.81%)	⬇️
app/marketing/mails.py	14.11% <0%> (-0.16%)	⬇️
... and 6 more

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