Docs: document apostrophe as an explicit string literal trigger

[sequba]

Context

Added section 'Forcing the string value type' to the 'Types of values' guide.

Unit tests have been added in #1161

How did you test your changes?

• unit tests pass
• local docs build

Types of changes

• Breaking change (a fix or a feature because of which an existing functionality doesn't work as expected anymore)
• New feature or improvement (a non-breaking change that adds functionality)
• Bug fix (a non-breaking change that fixes an issue)
• Additional language file, or a change to an existing language file (translations)
• Change to the documentation

Related issues:

Fixes #960

Checklist:

• I have reviewed the guidelines about Contributing to HyperFormula and I confirm that my code follows the code style of this project.
• I have signed the Contributor License Agreement.
• My change is compliant with the OpenDocument standard.
• My change is compatible with Microsoft Excel.
• My change is compatible with Google Sheets.
• I described my changes in the CHANGELOG.md file.
• My changes require a documentation update.
• My changes require a migration guide.

[github-actions]

Performance comparison of head (6d3111d) vs base (8a4bc46)

                                     testName |   base |   head | change
------------------------------------------------------------------------
                                      Sheet A | 558.96 |  559.3 | +0.06%
                                      Sheet B | 182.54 | 188.13 | +3.06%
                                      Sheet T | 163.42 |  162.8 | -0.38%
                                Column ranges |  565.6 | 567.55 | +0.34%
Sheet A:  change value, add/remove row/column |     41 |     42 | +2.44%
 Sheet B: change value, add/remove row/column |    292 |    304 | +4.11%
                   Column ranges - add column |    150 |    157 | +4.67%
                Column ranges - without batch |    584 |    599 | +2.57%
                        Column ranges - batch |     90 |     94 | +4.44%

[codecov]

Codecov Report

Merging #1334 (6d3111d) into develop (8a4bc46) will not change coverage.
The diff coverage is n/a.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #1334   +/-   ##
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  Coverage    97.36%   97.36%           
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  Files          169      169           
  Lines        14423    14423           
  Branches      3023     3023           
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  Hits         14043    14043           
  Misses         380      380