feat: add basic documentation to README.md

README.md

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 # math
+
+Web app that helps to perform some math computation, and tries to provide the intermediate steps taken.
+
+## Functions
+
+This app currently supports the following functions:
+
+### Determinant of a square matrix
+
+Frontend page: `/matrix`
+
+Frontend usage: `det [[1,2],[3,4]]` or `determinant [[1,2],[3,4]]`
+
+API: `/api/matrix/determinant?matrix=[[1,2],[3,4]]`
+
+Description: Calculates the determinant of a square matrix. Currently does not show the intermediate steps taken. The algorithm used is Laplace expansion which is `O(N!)`, so this could be slow for larger matrices.
+
+### RREF of a matrix
+
+Frontend page: `/matrix`
+
+Frontend usage: `rref [[1,2],[3,4]]`
+
+API: `/api/matrix/rref?matrix=[[1,2],[3,4]]`
+
+Description: Reduces a matrix to RREF. The algorithm used first reduces the matrix to a REF form, then to RREF form.
+
+## Caveats
+
+- Does not support fraction input
+- Supports RREF calculations where you have non-terminating decimals, such as the decimal representation of `1/3`. The output might contain somewhat long decimal representations but the idea is there.
+- Comes with usual floating point errors