docs(readme) added TOC (#1123)
docs(readme) added TOC (#1123)

generate table of contents for readme.

closes #1122
rattrayalex/prettier,rattrayalex/prettier,lydell/prettier,despairblue/prettier,arijs/prettier-with-tabs,despairblue/prettier,jlongster/prettier,arijs/prettier-miscellaneous,existentialism/prettier,yamafaktory/prettier,prettier/prettier,lydell/prettier,Skywalker13/prettier-space-parenthesis,lydell/prettier,existentialism/prettier,Skywalker13/prettier-space-parenthesis,prettier/prettier,arijs/prettier-with-tabs,existentialism/prettier,azz/prettier,Skywalker13/prettier-space-parenthesis,rattrayalex/prettier,prettier/prettier,arijs/prettier-miscellaneous,lydell/prettier,existentialism/prettier,azz/prettier,yamafaktory/prettier,arijs/prettier-miscellaneous,azz/prettier,Skywalker13/prettier-space-parenthesis,arijs/prettier-miscellaneous,azz/prettier,prettier/prettier