Large Copy Edit of stock options handbook page

The stock options page had several issues that I'm trying to resolve in this MR:

• Sections not in a logical order
• non-standard markdown that do not conform to the company standards.
• Some parts could be slightly clearer

The signification changes are (see image below as well):

• Introductory sections moved to the top (about your ownership/stock options), with grant levels a subsection of stock options.
• stock splits moved next to stock dilution
• exercising your options moved out one level, and option expiration and exercise window now subsections of it.
  • language slightly touched up to remove duplication of information here.
• how to exercise your stock options now a subsection of administration, since they are related (Carta usage)
  • language slightly touched up to remove duplicate information here.
• non-US employees section broken out into country-specific sections, to make it easier to find and easier to ignore information not related to your country.
• stock options board meeting reporting moved to the bottom, with the other "paperwork" guide (Procedures for issuing...), since these are not useful to the majority of GitLabbers (and targeted to only a few, or one, staffer)
• Questions moved down with references, as is more standard.
• The dual class structure ... section removed, since it was just a one sentence intro, and now clear with the new structure and touched up language here. This resulted in the 4 subsections moving left in the tree.
  • effect of dual-class moved to the top of the 4 items, as it's more logical this way.

Additionally:

• stock splits made clearer by adding (total value $10,000) to the example.

• the word effected changed to executed

• fixed typos, grammar mistakes, deleted extra blank lines

• the sample letter put in a code block (```) so that it copies and pastes properly now.

• option 5 in US employees with incentive stock options seemed to be wrong, so updated both 4. and 5.:

  • 4. Sell shares one year and a day after you exercised the options + less than two years from the original grant date.
  • 5. Sell shares one year and a day after you exercised the options + at least two years from the original grant date.
  • 4. Sell shares at least one year and a day after you exercised the options, but less than two years from the original grant date. (Updated)
  • 5. Sell shares at least two years from the original grant date. (Updated)

• double spaces after periods removed

• bullet lists made uniform throughout the page (hyphens instead of asterisks)