rewrite for MathJax v3

[pkra]

@zorkow has kindly created https:/mathjax/MathJax-src/blob/mathtools_package/ts/input/tex/mathtools/MathtoolsConfiguration.ts

[pkra]

First test looks ok. Found one case of multined that didn't work well yet:

\begin{equation}
 \begin{aligned}
[t] T_{{\mathbf{u}}, x} {\mathcal{V}}&= \begin{multlined}[t][.7\linewidth] \left\{ (\dot{{\mathbf{u}}}, \dot{x}) \in T_{\mathbf{u}}{\mathcal{U}}\times T_x {\mathbb{P}}^n\mathbin |\right. \\
 \left. \forall i, f_i \left( (\mathbf{1}_{\mathcal{U}}+ t \dot{u}_i + o(t))^{-1} (x+t \dot{x} + o(t)) \right) = o(t) \text{ as } t\to 0 \right\} \end{multlined}\\
 &= \left\{ (\dot{{\mathbf{u}}}, \dot{x}) \in T_{\mathbf{u}}{\mathcal{U}}\times T_x {\mathbb{P}}^n\mathbin |\forall i, f_i\left(x + t( \dot{x} - \dot{u}_i x) \right) = o(t) \text{ as } t\to 0 \right\}\\
 &= \left\{ (\dot{{\mathbf{u}}}, \dot{x}) \in T_{\mathbf{u}}{\mathcal{U}}\times T_x {\mathbb{P}}^n\mathbin |\forall i, \mathrm{d}_x f_i (\dot{x}) = \mathrm{d}_x f_i( \dot{u}_i x) \right\}. \end{aligned} \tag{17}
\end{equation}

V2

V3

Wth a different tag setup but the 2nd row's alignment is the problem: