docs: resolve some typos and adjust sentences structure

- Fix some typos in docs
- Adjust sentences structure
- Update words list

Signed-off-by: Yefeng Lin <yefeng.lin@arm.com>
Reviewed-by: Liangxing Wang <liangxing.wang@arm.com>
Reviewed-by: Nathan Brown <nathan.brown@arm.com>

Change-Id: I2dbe98237c618719eedf36d4a11cc4e92e6a26d9