Make url more recognizable apart from domain name

**Is your feature request related to a problem? Please describe.**
Problem: In some places we are not able to use the matrix.to domain (e.g. https://github.com/matrix-org/matrix.to/issues/177 , and matrix.to seems to be banned in mainland China). This poses a difficulty for these people to create/access matrix.to links. According to README, one can host their own matrix.to instance, but currently there is no way to identify a matrix.to link apart from the matrix.to domain ( https://matrix.org/docs/spec/appendices#matrix-to-navigation ). This makes it difficult for those using a client/bridge that does not support automatic conversion from a matrix.to link to e.g. a room invite. Thus, it helps to make a matrix.to link that can be on different domains (for directly opening in browser), and at the same time be conveniently recognized by clients (for quickly access the target pointed).

**Describe the solution you'd like**
Add some sort of identifier in the location part of the uri so that clients can recognize links from other domains as matrix.to links. (e.g. `https:///matrix-to/#/....`)

**Describe alternatives you've considered**
Matching the links against the current format, but ignoring domain name (i.e., matching `#//?`)

**Additional context**
N/A

Start by reading the README, the Matrix-to navigation specification, and issue 177 to understand hosting and domain constraints, then inspect how the current URI format is represented in the project. Done requires an agreed, domain-independent identifier that clients can recognize while preserving the existing link behavior and compatibility expectations.

Written by the indexing model from the issue text.