Misc changes and fixes

[AromaticWaffle]

Some fixes and changes for when I was looking at it a few months ago:
Changes affecting all versions:

• in 2nd last answer for p13, the pu answer just replaced namako with sin. Replaced with ko
• the video linked for the Arabic script in the x2 page isn't available any more, replaced with archive.org link
• sitelen pona page la the linja pona link needs to have https:// before
• update name and link of spp to sitelen sa
• renamed nasin nanpa Etan Itan (smh), and update img path

Changes for only en (and zh) version

• disclaimer on the "2 weeks to fluency" claim
• some updated descriptions on majuna, ku in dict & x1 due to lipu su
• add some more font recommendations & font example
• talk about sitelen jelo together with sitelen pilin

Oh and I endorse pr#28, merge it too while you're at it

[AcipenserSturio]

pona