improve hotfix documentation and mention px_scaling hotfix in jsPDF documentation

Author: HackbrettXXX

HOTFIX_README.md

@@ -3,51 +3,64 @@
 We sometimes bake-in solutions (A.K.A. hotfixes) to solve issues for specific use cases.
 
 When we deem a hotfix will not break existing code,
- will make it default behaviour and mark the hotfix as _accepted_,
- At that point the define can be removed.
- 
- To enable a hotfix, define the following member of your created PDF,
-where the pdf.hotfix field is the name of the hotfix.
-
-    var pdf new jsPDF(...);
-    pdf.hotfix.fill_close = true;
-  
+will make it default behaviour and mark the hotfix as _accepted_,
+At that point the define can be removed.
+
+To enable a hotfix, pass the `hotfixes` option to the jsPDF constructor:
+
+```js
+new jsPDF({
+  hotfixes: ["px_scaling"]
+});
+```
+
 # Active Hotfixes
+
 ## px_scaling
 
 ### Applies To
+
 jsPDF Core
 
 ### Description
+
 When supplying 'px' as the unit for the PDF, the internal scaling factor was being miscalculated making drawn components
-larger than they should be.  Enabling this hotfix will correct this scaling calculation and items will be drawn to the
+larger than they should be. Enabling this hotfix will correct this scaling calculation and items will be drawn to the
 correct scale.
 
 ### To Enable
+
 To enable this hotfix, supply a 'hotfixes' array to the options object in the jsPDF constructor function, and add the
 string 'px_scaling' to this array.
 
 #Accepted Hotfixes
+
 ## scale_text
 
 ### Applies To
+
 context2d plugin
 
 ### Affects
+
 Drawing and Filling Text when a scale transformation is active.
 
 ### Description
+
 jsPDF currently has no way to draw scaled text.  
 This hotfix scales the current font size by the x-axis scale factor.
- 
+
 ## fill_close
+
 ### Applies To
+
 context2d plugin
 
 ### Affects
-Filling paths 
+
+Filling paths
 
 ### Description
+
 In certain cases, closing a fill would result in a path resolving to an incorrect point.
-The was most likely fixed when we refactored matrix logic.  Enabling this hotfix will ignore a most-likely unneeded workaround.
- 
+The was most likely fixed when we refactored matrix logic. Enabling this hotfix will ignore a most-likely unneeded workaround.

src/jspdf.js

@@ -177,13 +177,15 @@ function TilingPattern(boundingBox, xStep, yStep, gState, matrix) {
  * @param {Object} [options] - Collection of settings initializing the jsPDF-instance
  * @param {string} [options.orientation=portrait] - Orientation of the first page. Possible values are "portrait" or "landscape" (or shortcuts "p" or "l").<br />
  * @param {string} [options.unit=mm] Measurement unit (base unit) to be used when coordinates are specified.<br />
- * Possible values are "pt" (points), "mm", "cm", "m", "in" or "px".
+ * Possible values are "pt" (points), "mm", "cm", "m", "in" or "px". Note that in order to get the correct scaling for "px"
+ * units, you need to enable the hotfix "px_scaling" by setting options.hotfixes = ["px_scaling"].
  * @param {string/Array} [options.format=a4] The format of the first page. Can be:<ul><li>a0 - a10</li><li>b0 - b10</li><li>c0 - c10</li><li>dl</li><li>letter</li><li>government-letter</li><li>legal</li><li>junior-legal</li><li>ledger</li><li>tabloid</li><li>credit-card</li></ul><br />
  * Default is "a4". If you want to use your own format just pass instead of one of the above predefined formats the size as an number-array, e.g. [595.28, 841.89]
  * @param {boolean} [options.putOnlyUsedFonts=false] Only put fonts into the PDF, which were used.
  * @param {boolean} [options.compress=false] Compress the generated PDF.
  * @param {number} [options.precision=16] Precision of the element-positions.
  * @param {number} [options.userUnit=1.0] Not to be confused with the base unit. Please inform yourself before you use it.
+ * @param {string[]} [options.hotfixes] An array of strings to enable hotfixes such as correct pixel scaling.
  * @param {number|"smart"} [options.floatPrecision=16]
  * @returns {jsPDF} jsPDF-instance
  * @description