README.md: add OCA footer
README.md: add OCA footer

I found this short OCA description in several repos. It's good to have it in the template.
ilyasProgrammer/maintainer-quality-tools,Endika/maintainer-quality-tools,Endika/maintainer-quality-tools,dreispt/maintainer-quality-tools,acsone/maintainer-quality-tools,acsone/maintainer-quality-tools,acsone/maintainer-quality-tools,ERP-Ukraine/maintainer-quality-tools,gurneyalex/maintainer-quality-tools,ERP-Ukraine/maintainer-quality-tools,dreispt/maintainer-quality-tools,ERP-Ukraine/maintainer-quality-tools,gurneyalex/maintainer-quality-tools,OCA/maintainer-quality-tools,ilyasProgrammer/maintainer-quality-tools,OCA/maintainer-quality-tools,dreispt/maintainer-quality-tools,OCA/maintainer-quality-tools,gurneyalex/maintainer-quality-tools