docs: Add mkdocs social meta tags

[cwhite911]

Added support for social meta tags for each page in mkdocs addressing part of issue #5162 .

docs: https://squidfunk.github.io/mkdocs-material/plugins/social/

<meta charset="utf-8">
      <meta name="viewport" content="width=device-width,initial-scale=1">
        <meta name="description" content="Overland flow hydrologic simulation using path sampling method (SIMWE).">
        <link rel="canonical" href="http://0.0.0.0:8000/grass-stable/manuals/r.sim.water.html">
        <link rel="icon" href="[favicon.ico](http://127.0.0.1:8000/grass-stable/manuals/favicon.ico)">
        <meta name="generator" content="mkdocs-1.6.1, mkdocs-material-9.6.2">
        <title>r.sim.water - GRASS GIS 8.5.0dev Reference Manual</title>
        <meta  property="og:type"  content="website" >
        <meta  property="og:title"  content="r.sim.water - GRASS GIS 8.5.0dev Reference Manual" >
        <meta  property="og:description"  content="Overland flow hydrologic simulation using path sampling method (SIMWE)." >
        <meta  property="og:image"  content="http://0.0.0.0:8000/grass-stable/manuals/assets/images/social/r.sim.water.png" >
        <meta  property="og:image:type"  content="image/png" >
        <meta  property="og:image:width"  content="1200" >
        <meta  property="og:image:height"  content="630" >
        <meta  property="og:url"  content="http://0.0.0.0:8000/grass-stable/manuals/r.sim.water.html" >
        <meta  name="twitter:card"  content="summary_large_image" >
        <meta  name="twitter:title"  content="r.sim.water - GRASS GIS 8.5.0dev Reference Manual" >
        <meta  name="twitter:description"  content="Overland flow hydrologic simulation using path sampling method (SIMWE)." >
        <meta  name="twitter:image"  content="http://0.0.0.0:8000/grass-stable/manuals/assets/images/social/r.sim.water.png" >

The images are not setup yet, but the background color looks nice.