[EP-351] Add Custom Font API

[a7medev]

Description of the change

Description goes here

Type of change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Related issues

Issue links go here

Checklists

Development

• Lint rules pass locally
• The code changed/added as part of this pull request has been covered with tests

Code review

• This pull request has a descriptive title and information useful to a reviewer
• Issue from task tracker has a link to this pull request

[InstabugCI]

	1 Warning
⚠️	Please include a CHANGELOG entry. You can find it at CHANGELOG.md.

Generated by 🚫 Danger

[codecov]

Codecov Report

Merging #292 (e0ac0e4) into master (7e8c8ff) will increase coverage by 0.14%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #292      +/-   ##
==========================================
+ Coverage   81.84%   81.98%   +0.14%     
==========================================
  Files          17       17              
  Lines         369      372       +3     
==========================================
+ Hits          302      305       +3     
  Misses         67       67              

Impacted Files	Coverage Δ
lib/src/modules/instabug.dart	98.75% <100.00%> (+0.04%)	⬆️

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