Flag/show estimated support/eol dates

[BiNZGi]

For some support/eol dates we use a calculation for estimation

• https://github.com/search?q=repo%3Aendoflife-date%2Fendoflife.date%20estimat&type=code
• https://github.com/search?q=repo%3Aendoflife-date%2Fendoflife.date+projected&type=code

For now we write a comment in the md file for our reference. The users of the website and api don't see that the date is estimated.

My idea is to flag those dates and show the user that the date is an estimation and perhaps also show how we calculated.

[marcwrobel]

Relates to #2245.