Yes, there is W3C (not to be confused with w3schools for the love of God). It is he who defines the standards of HTML and CSS. In the case of the JavaScript language, the standards are a committee linked to ECMA , an international association similar to ISO . In both cases, decisions are made by committees involving area experts, including representatives of browser manufacturers.
However, they basically define syntax patterns, defining what can be used in a certain technology or not. It is not the case of things like nomenclature and indentation, which are not officially standardized in the mentioned languages¹, being the final decision in charge of the developers themselves.
¹ In languages such as Python the indentation is part of the syntax itself, in which case it is defined in the standard.