gn: Add a newline to fix a bulleted list in README.md.

gn: Add a newline to fix a bulleted list in README.md.

Currently the bulleted list in the "What does 'done' mean?" section isn't
rendered (instead, it is shown as one paragraph with asterisks in the
middle). Adding a newline should fix this.

See https://chromium.googlesource.com/chromium/src/tools/gn/+/441de2f

Committed: https://crrev.com/92acc5eca80b1cbd6fcf18a81795c5b74f9d3f06
Cr-Commit-Position: refs/heads/master@{#331229}

[jbroman, 2015-05-22 15:31:29]

jbroman@chromium.org changed reviewers:
+ brettw@chromium.org

[jbroman, 2015-05-22 15:31:30]

Trivial, but annoyed me when I was reading docs.

[brettw, 2015-05-22 20:40:34]

lgtm

[jbroman, 2015-05-23 05:04:07]

The CQ bit was checked by jbroman@chromium.org

[commit-bot: I haz the power, 2015-05-23 05:04:18]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1153803002/1

[commit-bot: I haz the power, 2015-05-23 05:14:15]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-05-23 05:14:58]

Patchset 1 (id:??) landed as
https://crrev.com/92acc5eca80b1cbd6fcf18a81795c5b74f9d3f06
Cr-Commit-Position: refs/heads/master@{#331229}