doc: Edit About Zephyr for readability.
doc: Edit About Zephyr for readability.

Edit the content, adding bold text and headings for readability.
Revised the structure based on comments by developers.
Resubmitted to solve merge issues.

Change-Id: I7679eb7c71eab5cd18addcdb296c376923984494
Signed-off-by: L.S. Cook <2c8ffdbb27eb9faeeac367751f77804563aa8470@intel.com>
Signed-off-by: Rodrigo Caballero <e74c61adb7ade025bc8e83a25052d36636c989a9@intel.com>
bboozzoo/zephyr,mirzak/zephyr-os,rsalveti/zephyr,GiulianoFranchetto/zephyr,mirzak/zephyr-os,finikorg/zephyr,GiulianoFranchetto/zephyr,zephyriot/zephyr,explora26/zephyr,nashif/zephyr,holtmann/zephyr,pklazy/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,runchip/zephyr-cc3200,explora26/zephyr,mbolivar/zephyr,tidyjiang8/zephyr-doc,bigdinotech/zephyr,nashif/zephyr,sharronliu/zephyr,tidyjiang8/zephyr-doc,rsalveti/zephyr,coldnew/zephyr-project-fork,32bitmicro/zephyr,32bitmicro/zephyr,zephyrproject-rtos/zephyr,jamesonwilliams/zephyr-kernel,kraj/zephyr,holtmann/zephyr,coldnew/zephyr-project-fork,explora26/zephyr,punitvara/zephyr,punitvara/zephyr,zephyriot/zephyr,aceofall/zephyr-iotos,GiulianoFranchetto/zephyr,aceofall/zephyr-iotos,aceofall/zephyr-iotos,mirzak/zephyr-os,runchip/zephyr-cc3200,Vudentz/zephyr,pklazy/zephyr,coldnew/zephyr-project-fork,fbsder/zephyr,32bitmicro/zephyr,jamesonwilliams/zephyr-kernel,ldts/zephyr,zephyriot/zephyr,runchip/zephyr-cc3220,runchip/zephyr-cc3220,tidyjiang8/zephyr-doc,fractalclone/zephyr-riscv,bboozzoo/zephyr,aceofall/zephyr-iotos,bboozzoo/zephyr,mbolivar/zephyr,kraj/zephyr,GiulianoFranchetto/zephyr,erwango/zephyr,punitvara/zephyr,runchip/zephyr-cc3200,bigdinotech/zephyr,runchip/zephyr-cc3200,ldts/zephyr,explora26/zephyr,zephyrproject-rtos/zephyr,coldnew/zephyr-project-fork,runchip/zephyr-cc3220,fractalclone/zephyr-riscv,zephyriot/zephyr,erwango/zephyr,finikorg/zephyr,bigdinotech/zephyr,galak/zephyr,mirzak/zephyr-os,mbolivar/zephyr,rsalveti/zephyr,explora26/zephyr,32bitmicro/zephyr,fbsder/zephyr,fractalclone/zephyr-riscv,tidyjiang8/zephyr-doc,runchip/zephyr-cc3220,nashif/zephyr,GiulianoFranchetto/zephyr,jamesonwilliams/zephyr-kernel,pklazy/zephyr,aceofall/zephyr-iotos,bigdinotech/zephyr,rsalveti/zephyr,ldts/zephyr,Vudentz/zephyr,fbsder/zephyr,nashif/zephyr,runchip/zephyr-cc3220,Vudentz/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,kraj/zephyr,kraj/zephyr,fbsder/zephyr,fbsder/zephyr,ldts/zephyr,zephyriot/zephyr,finikorg/zephyr,rsalveti/zephyr,sharronliu/zephyr,kraj/zephyr,galak/zephyr,ldts/zephyr,sharronliu/zephyr,finikorg/zephyr,Vudentz/zephyr,mirzak/zephyr-os,sharronliu/zephyr,holtmann/zephyr,holtmann/zephyr,fractalclone/zephyr-riscv,bigdinotech/zephyr,jamesonwilliams/zephyr-kernel,Vudentz/zephyr,jamesonwilliams/zephyr-kernel,pklazy/zephyr,erwango/zephyr,galak/zephyr,32bitmicro/zephyr,mbolivar/zephyr,nashif/zephyr,finikorg/zephyr,fractalclone/zephyr-riscv,mbolivar/zephyr,holtmann/zephyr,bboozzoo/zephyr,punitvara/zephyr,erwango/zephyr,coldnew/zephyr-project-fork,runchip/zephyr-cc3200,galak/zephyr,bboozzoo/zephyr,pklazy/zephyr,zephyrproject-rtos/zephyr,erwango/zephyr,sharronliu/zephyr,tidyjiang8/zephyr-doc,punitvara/zephyr