Add fixes on the doc based on Jamie's Suggestions This is a follow up change based on comments Jamie provided in a previous change list: https://chromium-review.googlesource.com/c/angle/angle/+/3204430. Fixes include: 1. Wrap each line into 80 characters. 2. Add links to project files. 3. Add one more future work. 4. Modify the two simple wordings. Bug: angleproject:6508 Change-Id: I84a5694682d8871ebb46c4dfe245399021e0cff7 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3219715 Commit-Queue: Yuxin Hu <yuxinhu@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>