* Document calculation caching; and how to disable it and how to flush the cache
* Quoted text for string values beginning with `=`, so that they are still treated as strings and not as formulae
* Warning about assigning cells to variables
* Further warning about assigning cells to variables
The \PhpOffice\PhpSpreadsheet\Shared\Date class has support for setting an alternate timezone which affects the conversion of Excel Date timestamps in PhpSpreadsheet. This amendment is an effort to document this support.
We wrapped lines to make easier the source easier to read, and to have more manageable diffs.
This was done with something like:
```sh
pandoc --wrap=auto --atx-headers -f markdown -t markdown-fenced_code_attributes+pipe_tables+raw_html+intraword_underscores`
```
We aim for long pages instead of several small one, to make
`CTRL+F`ing easier and URL less prone to changes in the future.
There is still way to improve it though...
