[Feat]: Add markdown description to Sections

[aroundthecode]

Context

I manage a very complex and lonn helm chart with different options and use cases.
I've a wiki page explaining all different alternative and providind example to end users (500+ developers across differnet projects)
I'd like to move such page under helm-docs but I have to split the table in different subsection providing deiscriptionand exmples for each of them.

Checking current "sections" example I noticed you can split your value table in different section which it's super useful for very logn helm chart, but you cannot provide any additional info for each of them, just split the table.

Current Behavior

At the moment you cannot add any description to each section, just split the table and get an heading title

LikedBehavior

It would be extremely useful to be able to add subsequent comment or additional markup to each section so that you can explain section purpose or include code samples.

Possible Solution

1. Comments following the "@section" annotation should be aggregated under section title to be able to provide additional informations (standard markup, code sample, diagrams would all be useful)

2. (even better) - being able to filter individual section table into README.md.gotpl so that you can get only the desired table and use normal markdown to descrbe the whole section. This wuould avoid managind subsequent comment and leave all markdown syntax free in to the go template.