Update documentation about re-building on linux and number of workers

[mrbass21]

Description

• Update the -j option for make to default in the instructions to use all cores available instead of hard-coding '8'.
• Added a description in italics underneath to let the user know what the option does and how to override it. This follows a slightly different procedure from the linux build page, which exports a variable in the shell environment, but I think this is a little more straightforward.
• Added a Spanish translation using Google Translate
• Fixed some broken links in the en page
• Fixed broken links and missing pages to the pages I touched and used Google Translate to translate the content.

@pangolp There is text added here that would need translation to Spanish. If it is deemed redundant and authors wish to eliminate so we don't need a translation, that works for me, otherwise a Spanish translation will be needed. I can also change the grammar of the sentence if that makes translation more accurate.

[TheSCREWEDSoftware]

Spanish wise, I don't think i missed anything, @sudlud even if it's in spanish are you able to review the steps for linux? they should match the english currently