Indent paragraphed comments under the resp. bullet point for a feature

[virtualritz]

[features]
default = []
## the `spline_inverse()` code will check if the knot vector is
## monotonic in *debug* builds.
##
## ⚠️ This only works when using a *nightly* toolchain.
unstable = []

Expected MD output:

• unstable — the spline_inverse() code will check if the knot vector is monotonic in debug builds.

  ⚠️ This only works when using a nightly toolchain.

Actual MD output:

• unstable — the spline_inverse() code will check if the knot vector is monotonic in debug builds.

⚠️ This only works when using a nightly toolchain.

[ogoffart]

Yeah. Seems sensible

[virtualritz]

Cheers! 😄

[ogoffart]

v0.2.1 released with tyhe update.