A domain-specific language (DSL) is a computer language specialized to a particular application domain. This is in contrast to a general-purpose language (GPL), which is broadly applicable across domains. There are a wide variety of DSLs, ranging from widely used languages for common domains, such as HTML for web pages, down to languages used by only one or a few pieces of software, such as MUSH soft code. DSLs can be further subdivided by the kind of language, and include domain-specific markup languages, domain-specific modeling languages (more generally, specification languages), and domain-specific programming languages. Special-purpose computer languages have always existed in the computer age, but the term "domain-specific language" has become more popular due to the rise of domain-specific modeling. The line between general-purpose languages and domain-specific languages is not always sharp, as a language may have specialized features for a particular domain but be applicable more broadly, or conversely may in principle be capable of broad application but in practice used primarily for a specific domain. from Wikipedia
The second motivation behind mulder is to show that it can be easy to create your own domain-specific markup languages but above all that there are now excellent language workbench in order to obtain both a parser for this language but also the skeletons of the LSP server implementation allowing to obtain an excellent user experience in editors like monaco (code completion, linter, typechecking, ...).
Below a small video to explain LSP, it contains some demo to show the use of LSP within monaco.
Here a last video on what you can also envision for the use of domain-specific modeling languages to edit some contents within you website.
Do not hesitate to browse typefox website to envision how you could let user edit the content of a domain-specific markup languages.