Add Google Colab supported notebooks for examples

[shravanngoswamii]

Examples will run in CI -- generate both, a Documenter Markdown Page and Notebook with link to open in Google Colab:

• SSMProblems Kalman Filter -- Click Open in Colab at top
• GeneralisedFilters Trend Inflation -- Click Open in Colab at top

Closes #119

[github-actions]

SSMProblems.jl/SSMProblems documentation for PR #137 is available at:
https://TuringLang.github.io/SSMProblems.jl/SSMProblems/previews/PR137/

[codecov]

Codecov Report

❌ Patch coverage is 0% with 102 lines in your changes missing coverage. Please review.
✅ Project coverage is 79.52%. Comparing base (57320d5) to head (ee2a1d9).

Files with missing lines	Patch %	Lines
GeneralisedFilters/docs/literate.jl	0.00%	51 Missing ⚠️
SSMProblems/docs/literate.jl	0.00%	51 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #137      +/-   ##
==========================================
- Coverage   82.42%   79.52%   -2.91%     
==========================================
  Files          54       56       +2     
  Lines        2794     2896     +102     
==========================================
  Hits         2303     2303              
- Misses        491      593     +102     

Flag	Coverage Δ
GeneralisedFilters	82.10% <0.00%> (-1.55%)	⬇️
SSMProblems	26.66% <0.00%> (-16.20%)	⬇️

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[github-actions]

SSMProblems.jl/GeneralisedFilters documentation for PR #137 is available at:
https://TuringLang.github.io/SSMProblems.jl/GeneralisedFilters/previews/PR137/