Fix registerLanguage() issue in the code examples

[sequba]

Context

Code examples now check for registered languages before registering new ones.

How did you test your changes?

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:

1. Fixes [Bug]: Language already registered error in the i18n demo when switching between docs pages #1481

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 (43713d9) vs base (cdb234e)

                                     testName |   base |   head |  change
-------------------------------------------------------------------------
                                      Sheet A | 537.09 | 509.87 |  -5.07%
                                      Sheet B | 182.43 | 165.41 |  -9.33%
                                      Sheet T | 156.95 | 146.68 |  -6.54%
                                Column ranges | 532.24 | 514.99 |  -3.24%
Sheet A:  change value, add/remove row/column |  16.22 |  14.51 | -10.54%
 Sheet B: change value, add/remove row/column | 134.05 | 129.79 |  -3.18%
                   Column ranges - add column | 156.52 | 151.63 |  -3.12%
                Column ranges - without batch | 468.84 | 456.75 |  -2.58%
                        Column ranges - batch | 118.46 | 114.92 |  -2.99%

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.22%. Comparing base (cdb234e) to head (43713d9).
Report is 1 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #1484   +/-   ##
========================================
  Coverage    97.22%   97.22%           
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  Files          169      169           
  Lines        14523    14523           
  Branches      3080     3080           
========================================
  Hits         14120    14120           
  Misses         403      403