Building and flashing guide improvements

[gemenerik]

Main goal of this PR is to clarify that brushless uses a different defconfig

Major changes:

• Add brushless defconfig tab
• Remove roadrunner defconfig reference

Minor changes:

• Consistent code block formatting
• Retrieve number of processing units rather than assuming 12

[knmcguire]

There is unfortunately an issue, this will break tb docs of the toolbelt of building the documentation locally so it always need to be build as a submodule from the website. It won't know what the meaning of the tab group is otherwise

Another thing ofcourse is that now the markdown itself is less readable by itself. So unfortunately I do think that we need to discuss this break first before merging. We need to align on what is accepted within the repo doc files or not.

[gemenerik]

There is unfortunately an issue, this will break tb docs of the toolbelt of building the documentation locally so it always need to be build as a submodule from the website. It won't know what the meaning of the tab group is otherwise

Another thing ofcourse is that now the markdown itself is less readable by itself. So unfortunately I do think that we need to discuss this break first before merging. We need to align on what is accepted within the repo doc files or not.

The main point of this PR was to make it clear that for brushless people will need to use another defconfig. I removed the Jekyll liquid tags, let's discuss those another time!

[knmcguire]

You missed the

make flash

in the section of ###using a debug adapter. But rest looks good! From my part not a blocker so you can also merge as is.